Santa Monica City Council
November 18, 2025

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TABLE OF CONTENTS (continued)
SECTION ......................................................................................... PAGE # Table 4-3: Complete List of Action Items Developed by the Resiliency Planning Committee .................4-10 Table 4-4: Action Item Prioritization Results...........................................................................................4-12 Table 4-5: Hazard Mitigation Actions, City of Santa Monica ..................................................................4-14 Table 4-6: Project Evaluation Worksheet................................................................................................4-17 Table 5-1: Status of Action Items Completed or Ongoing Since 2016.......................................................5-6 Figures
Figure 1-1: City of Santa Monica (dark blue lines show approximate City boundary and study area).........1-4 Figure 2-1: Physiographic Map of Santa Monica and Surrounding Areas...................................................2-2 Figure 2-2: Average Annual Rainfall by Month, Recorded at the Santa Monica Pier Weather Station (historical values) and the Santa Monica Airport (“current normal”) ........................................2-5 Figure 2-3: Age Distribution of the Population in Santa Monica Compared to California ........................2-12 Figure 2-4: Major Roads In and Near Santa Monica ................................................................................2-18 Figure 3-1: Essential / Critical Facilities In and Near Santa Monica..........................................................3-10

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SECTION 1: INTRODUCTION
Throughout history, southern California residents, including people living in the city of Santa Monica and adjacent areas, have experienced a variety of natural hazards common to the area. Indigenous Americans and early European settlers who depended directly on the land for their food, housing and general welfare surely experienced many of the same natural hazards that impact the area today, including earthquakes, floods, wildfires, Santa Ana winds, landslides, and mudflows. Significant, unusual events were likely remembered and passed down from one generation to the next through oral histories. Unfortunately, most of these histories have been lost. In the late 1700s and 1800s, the natural events that disrupted the lives of the settlers were generally recorded in journals, letters, and newspaper articles. With the advent of photography, some of the impacts of natural hazards were recorded in photographs. Beginning in the early 1900s, as people began to attempt to understand and modify their environment to reduce the impact of natural hazards on the local population and the landscape, these events were also recorded in scientific publications. Today we rely on many of these sources to document the area’s past exposure to natural hazards. Given that the past is often the key to the present and the future, we use these accounts to assess the area’s potential future risks.

This is important because as the local population increases, natural hazards have the potential to pose an even higher risk to the population and economic welfare of the region. The impacts of climate change also add to the urgency of developing and adopting mitigation actions that will help the region become increasingly resilient to natural hazards.

As of 2024, if California were a country, it would rank as the fourth largest economy in the world with a gross domestic product of $4.08 trillion0F
1 , and the city of Santa Monica is a vibrant and
significant member of that economy. People originally from all over the United States and the world now call Santa Monica home because of its gentle Mediterranean climate, geographical attributes (the bay and ocean are at their doorstep, and the mountains are just a short drive away), and ample job opportunities. However, the southern California terrain is the product of powerfully active natural forces that form and tear down mountains at remarkable rates by geological standards, and when humans interact with this changing environment, there is a high possibility for the population to be negatively impacted. Thus, a natural event, such as an earthquake, has the potential to cause significant damage at the personal, local, and regional levels with the potential for loss of life, injuries, destroyed or impaired structures and infrastructure, loss of income, and the high costs associated with disaster response and recovery.

In addition to earthquakes, Santa Monica residents may also be impacted by windstorms, hurricanes, drought, slope failures, liquefaction, wildfires, soil erosion and expansive soils, and other natural hazards. Some of these, like hurricanes, occur very infrequently, whereas others, such as erodible, expansive and liquefiable soils, can be effectively mitigated with well-understood engineering methods. Being a coastal community, Santa Monica is also susceptible to coastal flooding resulting from a variety of phenomena, including storms, rogue waves, tsunamis, and sea-level rise due to global warming. The historical record and our current state of knowledge indicate that those hazards with the potential to cause the most damage in Santa Monica include earthquakes, strong winds, 1 Based on data obtained from https://www.gov.ca.gov/2024/07/15/californias-economy-leads-thenation/#:~:text=World%27s%20fifth%20largest%20economy%20California%20is%20the,to%20the%20U.S.%20 Bureau%20of%20Economic%20Analysis and
https://en.wikipedia.org/wiki/Economy_of_California#:~:text=The%20economy%20of%20the%20State%20of%2 0California,world%2C%20behind%20Germany%20and%20ahead%20of%20Japan, both accessed on March 14, 2025.

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wildfires, coastal and pluvial flooding (typically due to atmospheric rivers), and slope failures along the coastal bluffs. A very low-probability but high-risk event with the potential for loss of life and damage to infrastructure would be a tsunami caused by an earthquake on one of the faults offshore in Santa Monica Bay. These are the natural hazards that are covered in most detail in this document, given that it is possible to minimize the losses that result from these hazards through careful and robust planning, financial investment and community participation in the implementation of hazard reduction measures.

In alignment with the City’s Safety Element of the General Plan, this document also addresses some human-made issues; namely the management of hazardous materials and aviation hazards associated with the current use of Santa Monica airport, and inundation caused by the catastrophic failure of water retention structures. Thus, this report discusses the management of hazardous materials, including the use, storage, and transportation of hazardous materials through the city and in the Santa Monica airport facilities where hazardous substances were previously used, stored, and potentially discarded. Given that natural and human-made events typically only become a hazard when they interact with and impact the built environment and the people that live, work and play therein, possible mitigation actions that can be used to either avoid these hazards or to strengthen our built environment, including buildings and infrastructure, are also discussed.

WHY DEVELOP A LOCAL HAZARD MITIGATION PLAN?
The total global economic cost of damage caused by natural disasters in the past 40-plus years has increased significantly1F
2 ; the result of an overall increase in population, increased development and exposure, and the impact of human-caused climate change. Thus, the average global damage costs for the ten-year period between 1984-1993 is about $30.2 billion, whereas the average global cost for the ten-year period between 2014-20232F
3 is $168.2 billion. These figures capture the combined costs of drought, floods, extreme weather, extreme temperature, landslides, dry mass movements, wildfires, volcanic activity and earthquakes. Extreme weather, floods and earthquakes are responsible for most of the losses reported.

In the United States, between 1980 and 2024, there have been 403 weather-related disasters (drought, flooding, freeze, severe storm, tropical cyclone, wildfire, and winter storms) that have each caused more than $1 billion in damages. In fact, combined, these 403 disasters have caused $2,917.5 billion in damages (adjusted for inflation).3F 4 In California alone, during the same time
period, there were 14 drought events, 6 flood events, 3 freeze events, 4 severe storm events, and 19 wildfires that cost between $2 billion and $200 billion each.4F 5 The costs from the 2025 Palisades
and Eaton fires, including property damage, cleanup expenses, infrastructure repair, temporary housing, and business and employment losses, are currently estimated at $250-$275 billion, although the actual cost will likely not be known for years.5F 6 The available data also show that
weather-related losses in the past five years have been two- to three-times the losses experienced in the previous 40 years, showing that the costs from natural disasters are indeed increasing. 2 https://ourworldindata.org/grapher/damage-costs-from-natural-disasters; accessed March 17, 2025. 3 2023 is the last full year for which data are available as of March 17, 2025. 4 https://www.ncei.noaa.gov/access/billions/state-summary/US; accessed April 3, 2025. 5 https://www.ncei.noaa.gov/access/billions/state-summary/CA; accessed April 3, 2025. 6 https://www.accuweather.com/en/weather-news/accuweather-estimates-more-than-250-billion-in-damages-andeconomic-loss-from-la-wildfires/1733821, accessed July 30 2025.

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Earthquakes in urban areas are also costly. For example, the moderate-sized 1994 Northridge earthquake caused an estimated $20 billion in damages and more than $40 billion in economic losses.6F
7 Adjusted for inflation to 2025 dollars, these estimates amount to $43.5 billion and $87 billion, respectively.

These costs emphasize the importance of identifying effective ways to reduce a community’s vulnerability to disasters. Hazard mitigation plans assist in this endeavor by identifying resources, information, and strategies for risk reduction, while helping to guide and coordinate mitigation activities. With these aims in mind, the City of Santa Monica began work on its first Hazard Mitigation Plan (Plan) in June 2003; the document was completed and approved in 2004, and adopted in 2005. Many of the actions contained therein have since been implemented, helping the City be better prepared for future disasters.

The last update to the City’s Plan before this one was completed in 2016. This 2025 update to the City’s Plan builds on the 2016 document and incorporates the new requirements for these documents as spelled out in FEMA’s Local Mitigation Planning Policy Guide FP 206-21-0002 that became effective on 19 April 2023. In accordance with these requirements, this 2025 Plan does the following:

1. summarizes the natural disasters known to have historically impacted the southern California region, including in the past nine years since the last Plan was completed;

2. addresses how climate change is already impacting the community and presents the most recent peer-reviewed projections on climate change based on future greenhouse gas concentrations trajectories (the Representative Concentration Pathways (RCPs) adopted by the Intergovernmental Panel on Climate Change);

3. discusses the impact that the natural and human-caused hazards pose to the local community, including sensitive populations;

4. summarizes the mitigation actions that the City of Santa Monica has implemented since 2016 to reduce its vulnerability to natural hazards; and

5. provides a list of new strategies, activities and implementation actions that will further prepare the community to resist the impact of potential future natural and some humancaused hazard events, with an emphasis on equitable outcomes to the vulnerabilities identified.

This 2025 Plan also details the extensive public participation effort that was undertaken as part of the update. This included several meetings with an expanded advisory team comprised of several City staff members, representatives from the local school district and Santa Monica Community College, the local Chamber of Commerce, local hospitals, and neighboring City and County officials; an online survey open to all City residents, staff, and workers; and several community workshops presented both in-person and online. The survey and workshops were designed to update residents on the hazards and vulnerabilities identified during preparation of this Plan and its companion document, the City’s Safety Element of the General Plan, and obtain feedback on mitigation actions and strategies proposed by the residents, City staff and other stakeholders.

As with the original 2005 document and updates since, the 2025 Plan provides a set of action items 7 https://www.conservation.ca.gov/cgs/earthquakes/northridge; accessed April 3, 2025.

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that can help reduce the City’s risk from natural hazards through education and outreach programs, by fostering the development of partnerships, and by continuing to implement preventive activities (such as land use programs) that limit or guide development in areas at risk from natural hazards.

This 2025 Plan update discusses the City’s current hazard conditions, and provides actions that are consistent with current City standards and other relevant Federal, State or regional regulations, including FEMA requirements.

The resources and information contained within this Plan are meant to:
1) establish a basis for coordination and collaboration among City, County, and State agencies, non-governmental and private entities, and people that live and work in the city of Santa Monica;
2) identify and prioritize future mitigation projects designed to promote a more disaster-resilient and sustainable city, including reduced costs associated with disaster response and recovery; and
3) assist in meeting the requirements of federal assistance programs.

The Local Hazard Mitigation Plan works in conjunction with other City plans, including the City’s Safety Element of the General Plan and the City’s Emergency Operations Plan. The updates presented here will be reflected by reference in these other plans and documents.

Section 322 (a-d) of the Federal Disaster Mitigation Act of 2000 (DMA 2000) requires that local governments, as a condition of receiving Federal disaster mitigation funds, have a mitigation plan that:
1) describes the hazards, risks and vulnerabilities specific to the community, 2) identifies and prioritizes mitigation actions,
3) encourages the development of local mitigation, and
4) provides technical support for these efforts.

This Local Hazard Mitigation Plan for the City of Santa Monica serves to meet these requirements.

SCOPE AND IMPACT OF THE PLAN
Santa Monica’s Local Hazard Mitigation Plan affects the entire city (see Figure 1-1 below).

This Plan provides a framework for planning for the main natural hazards that have the potential to impact the Santa Monica area, in addition to some human-caused hazards identified during the preparation of the Safety Element of the General Plan. The resources and background information in the Plan are applicable City-wide, and the goals and recommendations can lay the groundwork for local mitigation plans and partnerships.

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Figure 1-1 – City of Santa Monica
(dark blue lines show the approximate City boundary and study area) Source: Google Maps (2024)

NATURAL HAZARD LAND USE POLICY IN CALIFORNIA
Planning for natural hazards should be an integral element of any city’s land use planning program.

All California cities and counties are required to have Safety Elements, one of seven mandatory elements of their General Plans, that document the natural hazards specific to the area and provide the framework by which ordinances to reduce these hazards are implemented. However, Safety Elements are typically updated only once every 15 to 25 years and are often superseded by other local and statewide planning regulations (in 2023 Santa Monica began the process of updating the City’s Safety Element that was last issued in 1995; City Council approved the Safety Element update at their meeting on February 11, 2025).

With the requirements for Local Hazard Mitigation Plans, the Federal Emergency Management Agency (FEMA) essentially exported the California municipal Safety Element idea to the rest of the United States, but with an expanded format that includes the requirement for a more publicly open and economically quantifiable planning process for community disaster reduction. FEMA also requires that Local Hazard Mitigation Plans be reviewed on a yearly basis and be updated every five years. Thus, whereas Safety Elements traditionally emphasize hazard mapping and develop forwardlooking land use planning policies to minimize those hazards, FEMA has directed that, following the hazard mapping effort, an emphasis be placed on hazard mitigation policies that are based on quantifiable vulnerability, loss, and risk analysis. FEMA also requires extensive public participation recognizing that without public education and citizen buy-in of mitigation needs, it is nearly impossible to mobilize the level of support necessary to fully begin to deal with multi-hazard mitigation over multi-decadal timescales. Given that climate change is expected to increase the frequency, duration and intensity of natural hazards, such as wildfires, extreme heat, drought, storms, heavy precipitation, and sea level rise, and that extreme weather hazards are now

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responsible for a significant portion of the costs from natural disasters in the United States, Local Hazard Mitigation Plans are now also required to address climate change.

The continuing challenge faced by local officials and State government is to keep the local hazard mitigation plans effective in responding to the changing conditions and needs of California’s diverse and growing communities without forgetting the effect that low-probability but high-risk natural events (such as major earthquakes, which can skip entire generations and are therefore likely to be dismissed over time) can have on the built environment. This is particularly true in the case of planning for natural hazards where communities must balance development pressures with detailed information on the nature and extent of hazards. Planning for natural hazards therefore calls for local plans to include inventories, policies, and ordinances to guide the safe development of areas that history shows can be greatly impacted by infrequent but large-magnitude natural hazard events.

These inventories should include the compendium of hazards facing the community, the built environment at risk, the personal property that may be damaged by hazard events, and most of all, the people who live in the shadow of these hazards. Mitigation actions and strategies need to provide for equitable outcomes that benefit the whole community, ensuring that underserved and socially vulnerable populations can recover from a disaster.

SUPPORT FOR NATURAL HAZARD MITIGATION
Like disaster preparedness, response, and recovery, all mitigation is local, and the primary responsibility for the development and implementation of risk reduction strategies and policies lies with local jurisdictions, including cities, counties, special districts and tribes. Local jurisdictions, however, are not alone. Partners and resources exist at the regional, State and Federal levels.

Numerous California and Federal agencies have a role in the research and public education about natural hazards and in natural hazard mitigation. Some of these key agencies include:
♦ The California Governor’s Office of Emergency Services (Cal OES) is responsible for disaster mitigation, preparedness, response, recovery, and the administration of federal funds to California’s local jurisdictions after a major disaster declaration. ♦ The California Geological Survey (CGS) and the U.S. Geological Survey (USGS) are responsible for geologic hazard characterization, public education, and the development of partnerships aimed at reducing risk. The Earthquake (Section 6), Tsunami (Section 7), Flooding (Section 8), and Landslide (Section 9) hazards sections of the Plan utilized maps, publications and consensus reports issued by the California Geological Survey and/or the U.S. Geological Survey.
♦ The Statewide California Earthquake Center (SCEC; used to be the Southern California Earthquake Center) gathers information about earthquakes, integrates this information on earthquake phenomena, and communicates this to end-users and the general public to increase earthquake awareness, reduce economic losses, and save lives. Many publications, research data and website information provided by SCEC were referred to in the Earthquake section of this report.
♦ The California Department of Forestry and Fire Protection (CAL FIRE) is responsible for all aspects of wildland fire protection on state lands, including administration of the state's private and public forests. Fire hazards prevention, suppression and rescue services in the

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city are provided by the Santa Monica Fire Department (SMFD). The Fire Hazards section (Section 10) of the Plan relies extensively on data provided by and available from both the CALFIRE and SMFD websites.
♦ The Federal Emergency Management Agency (FEMA) provides an extensive array of products and services designed to help communities prepare for disasters, in addition to providing assistance after a disaster. As part of these efforts, FEMA manages the National Flood Insurance Program, including the preparation and issuance of Flood Insurance Studies and Flood Insurance Rate Maps that delineate areas within the 100-year and 500-year flood zones. The Flooding Hazards section (Section 8) of this Plan relies on the FEMA-provided maps for Santa Monica, in addition to other resources that provide information on how to reduce the impact of flooding. Local Hazard Mitigation Plans like this one are mandated by FEMA. Thus, to facilitate the preparation of these documents FEMA has also prepared several guides and publications that are referred to in this document. FEMA also developed and distributes the GIS-based risk assessment software called HazUS (Hazards US), which can be used to estimate the risk from the natural hazards of earthquake, tsunami, hurricane, and floods. This software was used for this study to estimate the costs of four different earthquake scenarios, in addition to tsunamis, coastal flooding, and dam inundation. The results of these scenarios are summarized in the appropriate section of this report. ♦ The California Division of Water Resources (DWR) plans, designs, constructs, operates, and maintains the State Water Project; regulates dams; provides flood protection; and assists in emergency management. It also educates the public and serves local water needs by providing technical assistance. Dam inundation maps and other data prepared for and administered by the DWR and other departments under the DWR were used in the Flooding Hazards section of the Plan addressing inundation due to dam failure. ♦ The National Oceanic and Atmospheric Administration (NOAA) keeps records of storms and other natural hazard events for all regions of the United States, and conducts climate change research. The NOAA database was used extensively in the Tsunami, Flooding, Wildfire, and Climate Change and Extreme Weather sections (Sections 7, 8, 10 and 11) of this Plan.

NOAA’s National Weather Service also serves as the administrator of the NOAA Tsunami Program, supporting a worldwide network of tsunami detection, forecast, and warning systems to serve the US coastline.
♦ The Intergovernmental Panel on Climate Change (IPCC) is a United Nations project that compiles and publishes scientific studies related to climate change for the purpose of determining the state of knowledge on climate change, providing policymakers with data on the implications and potential future risks associated with climate change, and putting forward adaptation and mitigation options. Various reports issued by the IPCC were used in the Climate Change and Extreme Weather section (Section 11) of this Plan.

In addition to the agencies listed above, this report also used information extracted from various other sources including dozens of peer-reviewed scientific papers, books and news articles. The specific publications, books, and webpages referenced during the preparation of this Plan are identified in the appropriate section and are listed in Appendix I: References. Thus, information contained in the Plan is based on research from a variety of sources including those described above, with emphasis on data previously collected by the consultant for the Technical Background Report

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to the City’s Safety Element of the General Plan Update. The consultant was helped on this effort by staff from the City of Santa Monica, who conducted data research, facilitated steering committee meetings and public workshops, and developed the final Local Hazard Mitigation Plan.

The following section and subsections outline the methodology followed, including discussion of the specific requirements that the Plan addresses; the individuals that participated in the process of developing this Plan update; the research methods followed; and the public participation process.

PLAN METHODOLOGY
Guidelines and Requirements for Mitigation Plans
The following are the Federal requirements for approval of a Local Hazard Mitigation Plan:
♦ open public involvement, with public meetings that introduce the process and project requirements;
♦ the public must be afforded opportunities for involvement in identifying and assessing risk, drafting a Plan, and public involvement in approval stages of the Plan; ♦ community cooperation, with opportunity for other local government agencies, the business community, educational institutions, and non-profits to participate in the process; and ♦ incorporation of local documents, including the City’s General Plan, the Zoning Ordinance, the Building Codes, and other pertinent documents.

The following components must be part of the planning process:
♦ complete documentation of the planning process;
♦ a detailed risk assessment on hazard exposures in the community; ♦ a comprehensive mitigation strategy, which describes the goals and objectives, including proposed strategies, programs and actions that can be implemented to reduce or minimize long-term vulnerabilities;
♦ a plan maintenance process, which describes the method and schedule of monitoring, evaluating and updating the Plan and integration of the Local Hazard Mitigation Plan into other planning mechanisms;
♦ formal adoption by the City Council; and
♦ plan review by both FEMA and Cal OES.

These requirements are spelled out in greater detail in the following sections of the Plan and supporting documentation.

Input From the Resilience Planning Committee
The Resilience Planning Committee (RPC) guided the development and update of the Local Hazard Mitigation Plan, and played an integral role in developing the mission, goals, and action items. The committee consisted of representatives from the following agencies in the City of Santa Monica:
 City of Santa Monica Manager’s Office, Office of Emergency Management  City of Santa Monica Fire Department, Fire Prevention  City of Santa Monica Public Works Department, Administration

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 City of Santa Monica Public Works, Engineering and Street Services  City of Santa Monica Community Development Department, City Planning  City of Santa Monica Information Services Department, GIS Input on specific sections of the Plan was also provided by representatives from the following agencies and organizations:

City of Santa Monica Departments
 City of Santa Monica Attorney’s Office
 City of Santa Monica Manager’s Office, Office of Emergency Management  City of Santa Monica Community Development Department, Building and Safety  City of Santa Monica Community Development Department, City Planning  City of Santa Monica Department of Transportation
 City of Santa Monica Finance Department
 Santa Monica Fire Department, Fire Administration
 Santa Monica Fire Department, Fire Prevention
 City of Santa Monica Housing and Human Services Department  City of Santa Monica Information Services Department
 City of Santa Monica Police Department
 City of Santa Monica Public Works Department, Administrative Services  City of Santa Monica Public Works Department, Engineering & Street Services  City of Santa Monica Public Works Department, Office of Sustainability and the Environment  City of Santa Monica Public Works Department, Santa Monica Airport  City of Santa Monica Rent Control Department
Regional Government Partners
 City of Los Angeles, Emergency Management Department
 County of Los Angeles, Office of Emergency Management Local Educational Institutions
 Santa Monica College (SMC)
 Santa Monica-Malibu Unified School District (SMMUSD)
Local Hospitals
 University of California, Los Angeles (UCLA) Health/Santa Monica Medical Center  Providence Saint John’s Health Center
Local Non-Profits
 American Red Cross
 Westside Food Bank
Local Business Organizations
 Downtown Santa Monica Business Improvement District
 Santa Monica Chamber of Commerce
 Santa Monica Travel and Tourism

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Hazard Specific Research
Santa Monica’s consultant and City staff collected data and compiled research on the natural hazards that have historically impacted the southern California region, with an emphasis on the Santa Monica area, and identified several hazards that have the potential to cause damage in the city.

These include earthquakes, tsunamis, coastal floods, inundation due to dam failure, slope failures or landslides, windstorms, sea-level rise, and extreme weather events related to climate change.

Human-caused incidents that also have the potential to result in localized damage to the community include urban fires, releases of hazardous materials and aircraft accidents. Noise pollution related to the airport was identified as a nuisance. Other potential hazards that were identified by the Resilience Planning Committee members that are not addressed in this document include pandemics, terrorist acts, civil unrest, active shooter incidents, riots and protests, and cyberattacks to infrastructure. The City has guidelines that address several of these potential hazards already in place and chose to align this Plan’s hazards with those in the City’s Safety Element, approved in 2025. Future versions of this Plan may include some of these subjects.

As mentioned previously, research materials used in the preparation of this Plan include publications by federal agencies such as FEMA, USGS and NOAA; state agencies such as CGS, Cal OES and CALFIRE; the City of Santa Monica’s Safety Element, and other sources. The City’s consultant conducted research by referencing historical local sources, interviewing City of Santa Monica employees and residents who provided invaluable data regarding past local disasters, and locating information specific to the City of Santa Monica in historical documents.

City of Santa Monica’s staff proposed and then evaluated the feasibility and potential effectiveness of the mitigation activities, resources and programs, and potential action items presented in this updated Plan. This evaluation was based on their experience in implementing the action items in the Safety Element and the previous 2016 Plan, and based on feedback from stakeholder surveys and interviews.

Public Participation Process and Stakeholder Surveys
As mentioned earlier, the City of Santa Monica began preparation of the first, original version of its Local Hazard Mitigation Plan in 2003; the Plan was completed and approved by both the State and FEMA in 2004, and adopted in 2005. Work on the first update of this original document began in the summer of 2013, with the final revised update adopted in March 2016.

Work on this 2025 updated Plan began on June 27, 2023 when the City of Santa Monica entered in a contractual agreement with Earth Consultants International, Inc., the consultant retained to work with the City on preparing this update. The City’s Office of Emergency Management identified the City departments and local agencies that would be part of the Resilience Planning Committee (RPC), and the kick-off meeting for the project was held at the EOC’s meeting room on September 14, 2023.

Work on the various sections of the Plan, including HazUS loss estimations for several earthquake, tsunami and flood scenarios began in earnest thereafter, with drafts of several of the hazard sections submitted for review by the City throughout 2024 and into early 2025. The findings of the HazUS loss estimations were presented to the RPC at a workshop on January 23, 2024.

Work on the Technical Background Report to the Safety Element, and the Safety Element proper, companion documents to the Plan, was conducted in parallel, with similar hazards addressed in all these documents. As part of the public participation component for both the Safety Element and the

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Local Hazard Mitigation Plan, a survey was posted online that asked respondents to weigh in on the natural and environmental hazards of most concern to them and their perceived level of preparedness for a variety of hazards. The online survey was available in English and Spanish and paper copies in both languages were made available at both the Main Library and the Pico Branch Library. The results of that survey informed the direction of both the Safety Element and the Plan.

The Safety Element was completed in August 2024, with City Council approving the document on February 11, 2025. The Final Safety Element, Technical Background Report to the Safety Element, and Vulnerability Assessment for the Safety Element can be accessed here.

Public workshops to discuss the Local Hazard Mitigation Plan were conducted on April 30 and May 2, 2024. The April 30 workshop materials were prepared in Spanish with a real-time translation available to attendees in an effort to reach and inform the City’s Spanish-speaking residents. An online version of the presentation was also held on May 22, 2024. The meeting was recorded and placed on YouTube. Availability to this YouTube recording was advertised in the City of Santa Monica News website (SaMoNews) and a several other City of Santa Monica webpages. As of March 19, 2025, the online presentation had been viewed 278 times; and as of August 5, 2025, the presentation had been viewed 318 times. The PowerPoint presentation slides are included in Appendix B.

Following the public workshop presentations, another meeting with the RPC was held on May 15, 2024. After a PowerPoint presentation that summarized the objectives of the Plan and the findings regarding the hazards covered in the Plan was completed, the committee members were asked to break out into groups and develop a list of potential action items intended to reduce or mitigate the hazards assigned to them. During the last 90 minutes of the meeting, the break-out groups discussed their recommendations, and the top recommendations for each hazard category were identified.

Following this meeting, a survey was prepared and distributed to all committee members and City staff asking for the action items identified to be ranked according to priority. The action items and the priority ranking based on this survey are presented in Section 4 of this report.

It is important to note that while work on this Plan update was being conducted, the City of Santa Monica and adjacent areas were impacted by several natural disasters. The most significant and costly of these events include:

1. Between December 2022 and March 2023, the southern California region experienced a series of atmospheric rivers that dropped significant precipitation on the local mountains, causing debris flows and landslides locally. At least three Disaster Declarations that included Los Angeles County were issued in response to these storms.

2. On August 20, 2023, the southern California region was impacted by heavy rain and strong winds brought on by Tropical Storm Hilary, with numerous areas reporting street flooding, mudslides and debris flows.

3. Between February 4 and February 8, 2024, the southern California region was impacted by a slow-moving atmospheric river that dropped between 6 and 12 inches of rain, again causing flooding, mudslides and debris flows.

4. On December 9-10, 2024, the area experienced strong Santa Ana winds that fanned the Franklin Fire that ultimately consumed more than 4,000 acres in Malibu. The Santa Monica area was impacted by both ash and smoke from those fires, and traffic associated with the closure of Pacific Coast Highway (PCH).

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5. On January 7-8, 2025, another round of extremely strong Santa Ana winds hit the southern California region and fanned the Palisades and Eaton fires. The Palisades fire extended south to within 1/3 mile of the city of Santa Monica. Much of the city north of Montana Avenue was in an evacuation zone, with mandatory evacuation orders issued for all residents on San Vicente Boulevard and all areas north to the City limits in place for almost a full week.

Warning notifications were issued for areas between San Vicente Boulevard and Montana Avenue, from 11th Street to PCH, and from 11th Street to 26th Street, and from Montana Avenue to Wilshire Boulevard between 10th Street and PCH. Ash and smoke from the fire impacted the community and especially vulnerable populations. The winds cost the City over $180,000, with these expenses associated with the clearing of almost 50 fallen trees and 122 tree limb failures, and the transport of 375 tons of vegetation debris to appropriate landfills. Short- and long-term effects of these fires include a decrease in local tourism and business activity, and an increased demand on Santa Monica’s rental market, resulting in rising rents. Santa Monica also provided and continues to provide a refuge for many displaced by the fires, potentially causing additional strain on the City’s real-estate market.

City emergency management personnel working on this Plan were the primary responders to these regional events, participating in mitigation, response and recovery activities. In addition, sections of the report that had already been drafted were updated after these events occurred, triggering additional revisions. The fires in 2024 and 2025 in particular, occurred after the action items for this next five-year cycle had been identified and prioritized. As a result, new action items that address wildfires that had not been originally identified as priorities were added to this Plan. These actions were partly based on public feedback during wildfire community meetings and during the Safety Element Council presentation. This is also discussed in Section 4.

PLAN STRUCTURE
The resources and information cited in the Plan provide a strong local perspective and help identify strategies and activities to make the City of Santa Monica more disaster-resilient.

Each section of the Local Hazard Mitigation Plan provides information and resources to assist City staff and the public in understanding the hazard-related issues facing Santa Monica’s citizens, businesses, and the environment. Combined, the sections of the Plan work together to create a document that guides the mission to reduce risk and prevent loss from future natural hazard events and some human-made situations.

The structure of the Plan enables the user to refer to specific sections of interest. It also allows the City to review and update specific sections as needed when new data become available. The ability to update individual sections of the Plan places less of a financial burden on the City. Decisionmakers can allocate funding and staff resources to selected pieces in need of review, thereby avoiding a full update, which can be costly and time-consuming. New data can be easily incorporated, resulting in a Local Hazard Mitigation Plan that remains current and relevant to the City of Santa Monica.

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Santa Monica’s Local Hazard Mitigation Plan is organized in three volumes, as follows:

1. Volume I contains the Executive Summary followed by Sections 1 through 5: introduction, Community Profile, Risk Assessment, Goals and Action Items, and Plan Maintenance.

2. Volume II discusses the hazards addressed in the document, with each of the main hazards identified assigned a specific section.

3. Volume III includes several appendices that support the information presented in Volumes I and II, including documentation on the public participation effort, resources, and list of references, among others.

Updates to these volumes include additions summarizing natural hazard events that impacted the southern California area and Santa Monica between 2016 and January 2025, and changes or updates to the regulations issued by both the Federal and State governments aimed at reducing the impact of natural hazards. Each section of the Plan is discussed further below, with an emphasis on the specific changes made as part of this update.

Volume I: Mitigation Action Plan
Executive Summary: Five-Year Action Plan
The Five-Year Action Plan provides an overview of the Local Hazard Mitigation Plan’s mission, goals, and action items.

Section 1: Introduction
The Introduction describes the background and purpose of developing the Local Hazard Mitigation Plan for the City of Santa Monica.

Section 2: Community Profile
This section presents the history, geography, demographics, and socioeconomics of the city of Santa Monica, with emphasis on the most recently available census data (2020 and 2022 American Community Survey) and development changes in the City since 2016. This section serves as a tool to provide an historical perspective of natural hazards in Santa Monica, and a springboard to understand how natural hazards can impact the City in the future.

Section 3: Risk Assessment
This section provides information on hazard identification, vulnerability and risk associated with the natural hazards, and some human-made hazards, found to pose a risk to the city of Santa Monica.

Section 4: Goals and Action Items
This section is the “Policy Document” that enumerates the specific action items that Santa Monica has chosen to undertake to further reduce its risk to the hazards described in Volume II of the document. Section 4 is completely new, presenting the action items that the City has prioritized for possible implementation during the five-year period between 2025 and 2030.

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Section 5: Plan Maintenance
This section provides information on Plan implementation, monitoring and evaluation, and lists the action items and hazard-reduction activities completed by the City in the past nine years (2016-2024 inclusive).

Volume II: Hazard Specific Information
Hazard-specific information on six major categories of natural hazards is addressed in this Plan.

Chronic hazards, such as coastal and pluvial flooding and strong Santa Ana winds, occur with some regularity and may be forecast through scientific methods. Catastrophic hazards do not occur with the frequency of chronic hazards, but notwithstanding, they can have devastating impacts on life, property, and the environment. In southern California, because of its geology and terrain, earthquakes, floods, wildfires, landslides and windstorms have the potential to be both catastrophic as well as chronic.

The hazards addressed in the Plan include:

Section 6: Earthquakes—including ground shaking, fault rupture, liquefaction, and slope failure due to ground shaking.

Section 7: Tsunamis—including both tele-tsunamis and locally generated tsunamis.

Section 8: Floods—including coastal flooding due to storms, fluvial (riverine) flooding, and pluvial (urban) flooding associated with atmospheric rivers. This section also discusses inundation due to catastrophic failure of above-ground water storage tanks and reservoirs.

Section 9: Landslides—including rock falls, topples, slides, spreads, mud or debris flows, and soil slips. This section also describes the geologic setting and geologic units that underlie Santa Monica.

Section 10: Wildfires and Urban Fires—including the wildfires that have recently impacted the hills north of Santa Monica; structure fires and after-earthquake fires. The section also describes the model ordinances and codes used to reduce the fire hazard, and the City’s fire suppression capabilities.

Section 11: Climate Change and Severe Weather—including extreme heat, drought, sea-level rise, and severe windstorms. Each of these phenomena are described within both a historical and future context specific to Santa Monica with an emphasis on the effects that climate change may have on the frequency and intensity of these events, and the impact that these weather events can have on socially vulnerable populations.

Section 12: Hazardous Materials Management—new section that addresses the potential release onto the environment of hazardous materials due to leaking underground storage tanks, transportation accidents, damaged pipelines, earthquakes, and the use of hazardous materials in household. The section describes past releases of potentially hazardous materials in Santa Monica and the resources available to reduce and manage these events.

Section 13: Airport Hazards—new section that discusses aviation accidents and incidents, noise nuisance related to airport traffic, and the past and current use of hazardous materials at the Santa Monica Airport.

Each of the hazard-specific sections includes information on the history, hazard causes and characteristics, hazard and vulnerability assessment, risk analysis, and local, state, and national resources available to mitigate or reduce the impact of these hazards. Goals and action items aimed

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at reducing these hazards, if identified as priorities for the next five-year cycle, are provided in Section 4.

Volume III: Resources
The Plan appendices are designed to provide users of Santa Monica’s Local Hazard Mitigation Plan with additional information to assist them in understanding the contents of the Mitigation Plan, and potential resources to assist them with implementation.

Appendix A: Master Resource Directory
This appendix provides a resource directory, which includes City, regional, State, and national resources and programs that may be of technical and/or financial assistance to the City of Santa Monica during Plan implementation. Most of the same data are also included at the end of Sections 6 through 11, where resources specific to the hazards addressed are listed.

Appendix B: Public Participation Process
This appendix includes specific information on the various public processes used during development of the 2025 Plan, including meetings, public workshops, and presentations made during the update process, and the individuals that participated in the process of developing the 2025 Plan update. Copies of the PowerPoint presentations prepared for the meetings and workshops are included here. Appendix B also includes the response to comments received from the public posting of the final draft of the document in AugustSeptember 2025.

Appendix C: Benefit Cost Analysis
This appendix describes FEMA's requirements for benefit cost analysis in natural hazards mitigation, as well as various approaches that FEMA recommends be used for conducting an economic analysis of proposed mitigation activities.

Appendix D: List of Acronyms
This appendix provides a list of acronyms for City, regional, state, and federal agencies and organizations that may be referred to within Santa Monica’s Local Hazard Mitigation Plan.

Appendix E: Glossary
This appendix provides a glossary of terms used throughout the Plan.

Appendix F: California Disasters
This appendix lists major California disasters since 1950. This list was updated to include events that occurred between 2016 and through January 2025.

Appendix G: List of Dams
This appendix provides a list of major dams and reservoirs in Los Angeles County.

Appendix H: Maps
This appendix contains the maps referenced throughout the Plan.

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Appendix I: References
This appendix lists the references (plans, studies, technical reports and websites) used in the preparation of the Plan.

Appendix J: Plan Adoption
Documentation regarding the formal adoption of the 2025 Plan Update.

CHANGES FROM THE 2016 PLAN
Several sections of the 2025 Plan Update have been modified from the 2016 Plan. Changes made to specific sections of the Plan are summarized further below.

Section 1: Summarizes the process by which the 2025 Plan was created, with emphasis on the review process and the opportunities provided for City Staff and the public to review and provide feedback on the document.

Section 2: This section was expanded, providing a more detailed description of Santa Monica’s physiographic location to better set the stage for why Santa Monica is susceptible to the natural hazards covered in this document. The population and demographics sections were completely revised and expanded to provide a more thorough analysis of the City’s population based on data from the 2020 Census and 2022 American Community Survey.

Section 3: This section of the Plan was enhanced to identify in table format those hazards that the Resilience Planning Committee agreed pose a potential hazard to the City, with rankings for probability of occurrence and potential level of risk. This section also identifies the critical facilities in the city and their vulnerability to the various natural hazards described in the Plan.

Section 4: The Action Items portion has been completely revised and updated to present the mitigation measures that the City has identified as current priorities in its effort to reduce its risk to the natural and human-made hazards identified. The action items are classified into three groups as follows: 1) action items that are already being implemented on an on-going basis, as part of the development or re-development process; 2) action items to be implemented in the short-term, that is, the next 5-year cycle (2025-2030); and 3) long-term action items that the City is considering for implementation in the next approximately 10 years that reference long-term policies and programs identified in the updated 2025 Safety Element of the General Plan.

Section 5: This section was completely updated to discuss how the Plan will be maintained in the next 5 years, and how progress on natural hazard reduction efforts will be measured. This section also identifies those action items listed in the 2016 Plan that have already been completed or are being implemented on an on-going basis.

Section 6: The earthquake hazards section was updated to describe the more recent earthquake events that impacted the southern California area through January 2025; provide a detailed description of the local and regional faults that could cause an earthquake that would be felt in Santa Monica; and more significantly, include the 2018 Alquist-Priolo Earthquake Fault Zones (APEFZ) for the Santa Monica fault issued by the California Geological Survey in 2018. Any property in Santa Monica located within an APEFZ identified by the State is now required to conduct a fault investigation if the property is to be re-developed into a structure more than two-stories high. This

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section also presents the findings of HazUS-based loss estimations conducted for the city addressing the impact that an earthquake on the Santa Monica, San Andreas, Newport-Inglewood or Palos Verdes faults would have on the city, including estimates of damage to structures, critical and essential facilities; casualties; and economic losses. The previous plan provided data on the structures impacted by the Northridge earthquake, but did not provide loss estimates for a plausible future earthquake scenario.

Section 7: The updated tsunami hazards section discusses significant tsunami events including the December 26, 2004 Indian Ocean earthquake and tsunami that killed more than 220,000 people worldwide. This catastrophe prompted the development and deployment of an international tsunami monitoring system, and led several communities, including many cities in California, to identify evacuation routes and develop tsunami training programs. The updated section describes the potential for southern California to be impacted by tsunamis generated by any of several subducting faults along the Pacific Ring of Fire, which would create a distant-source tsunami (teletsunami), and by faults in the Santa Monica Bay. An earthquake on a local fault could have a catastrophic effect on the city. To evaluate the risk of both a teletsunami and a local tsunami on Santa Monica, this section includes HazUS-based loss estimates for a tsunami originating in the Aleutian Islands in Alaska, and a local tsunami caused by an earthquake on the offshore section of the Palos Verdes fault in Santa Monica Bay.

Section 8: The flood hazards section was updated to describe the storms that have impacted the Los Angeles region, including Santa Monica between 2014 and January 2025, with an emphasis on atmospheric rivers. The impacts of tropical storm Hilary were also discussed. The revised section also provides HazUS-based loss estimates for Santa Monica as a result of the catastrophic failure of Stone Canyon dam and reservoir, a water storage facility owned by the City of Los Angeles in the hills above Bel Air that, if it failed, could inundate a portion of Santa Monica along its eastern boundary, near and surrounding the Interstate 10 (I-10).

Section 9: The landslides section was significantly modified to include a more in-depth description of different types of slope failure, and includes a slope distribution map and a slope instability map for Santa Monica. The maps identify those areas in Santa Monica that are susceptible to slope damage, such as the properties along the city’s northern boundary, the hillside areas south of the Brentwood Country Club, the coastal bluffs facing the Pacific Coast Highway (PCH), the slopes facing the I-10, and the hillside areas north of Penmar Golf Course. The section also discusses in detail the mitigation actions, both past and ongoing that have been implemented to reduce slope failures along the coastal bluffs in Pacific Palisades Park.

Section 10: The renamed wildfire and urban fire section was updated significantly and includes a description of the most significant wildland fires in California that have generated an increased awareness of this issue in light of climate change, triggering changes in regulations and insurance practices. The regulatory context and Federal, State and local programs that have been developed to mitigate the hazard of wildfires are discussed extensively with an emphasis on how these programs apply to and are being implemented in Santa Monica. The 2025 Plan also discusses in far more detail the potential for structure fires to occur in the city, especially in mixed-use areas and in older neighborhoods, and the potential for fires to occur following an earthquake.

Section 11: The climate change and severe weather section combines and expands on the severe windstorm/thunderstorm and climate change/sea level rise sections in the 2016 Plan, and relies on

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the more recent projections of greenhouse gas concentrations and sea level rise issued in 2022 by the Intergovernmental Panel on Climate Change (IPCC) and other organizations. The section summarizes significant weather events that have impacted Los Angeles County between 2016 and January 2025, with emphasis on those events that have occurred near Santa Monica.

Additional Changes: The 2016 updated Plan addressed two human-related hazards related to community events and the Exposition Light Rail. The Community Events section discussed the potential impacts of a large group of people concentrating in a limited geographic area, including increased chance for an act of terrorism or civil unrest to occur, and the potential for a large number of casualties if a community event coincided with a natural disaster, such as an earthquake, severe weather event, or structural fire in a high-occupancy building. Action plans designed to deal with hazards associated with large groups of people were developed and are now routinely implemented by the City as needed.

The Exposition Light Rail section discussed the risks associated with train accidents in an urban environment where the train lines extend through the city rather than around it. Some of the issues mentioned included accidents due to human error, equipment malfunction, and the potential impact of what at the time was a proposed project on existing street widths, especially the lack of 20-footwide lane for fire engine access. Several mitigation measures to be implemented by the various responsible agencies including the Exposition Construction Authority, METRO, Santa Monica City staff, and the Santa Monica Fire Department were identified and included in the design and construction, effectively mitigating several of the concerns that the City had originally identified. As a result, these hazards are not covered in the 2025 Plan.

Instead, the 2025 Plan includes two new sections on human-caused hazards associated with hazardous materials and the use and potential reuse of the Santa Monica airport facilities. These sections replace the sections that addressed hazards related to community events, and the construction and use of the Exposition Light Rail that were included in the 2016 Plan. Santa Monica has a Community Events Committee that addresses the permits and deployment of resources necessary to manage most community events in the City, and has developed a series of special operations plans to address a variety of events that would result in large groups of people converging in a small geographic area. The Exposition Light Rail section in the 2016 Plan enumerated the series of actions that the Los Angeles County Metro, City of Santa Monica staff and various other organizations implemented in the design-build process to make the light rail and associated stations compatible with street traffic, pedestrian safety, and ability of the Fire Department and other emergency response organizations to respond to emergencies as needed.

The Appendices were updated as needed to reflect the most current information, with emphasis on changes made between 2016 and 2024 (or January 2025 where the data were available).

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SECTION 2: COMMUNITY PROFILE
WHY PLAN FOR NATURAL HAZARDS IN THE CITY OF SANTA MONICA? Earthquakes, rainstorms, and strong winds have previously exposed the Los Angeles metropolitan area, including the city of Santa Monica, to the financial and emotional costs of recovery. These same natural hazards, and other natural and human-made hazards described herein, have the potential to pose a future negative impact on the city. Santa Monica is essentially “built-out,” with population growth generally associated with the replacement of low-density housing with mediumand high-density housing.

Given that natural hazards are inevitable, and that populations in hazardous areas are increasing in response to development, there is a need to develop strategies, coordinate resources, and increase public awareness to reduce the risk and losses from future natural hazard events. Identifying the risks posed by natural hazards, and developing strategies to reduce their impact can assist in protecting life and property. In Santa Monica, local residents have worked together with City staff and other stakeholders to create this Local Hazard Mitigation Plan (LHMP) document that addresses the potential hazards of most concern to Santa Monica’s residents.

GEOGRAPHY AND THE ENVIRONMENT
Physiographic Location and Description
The city of Santa Monica is 8.4 square miles in area and is located in the northwestern margin of the Los Angeles Basin. Santa Monica is bordered by communities that are part of the city of Los Angeles to the north, east, and south, and by the Pacific Ocean to the west (Figure 2-1). The city’s coastal location, along one of the widest stretches of beach along the Santa Monica Bay region, make Santa Monica both a sought-after living locale and a top tourist destination.

Santa Monica is located at the foothills of the Santa Monica Mountains, with the northern half of the city sitting on a broad, gently south-sloping alluvial fan that was formed by streams draining the mountains to the north. These mountains, together with the San Gabriel Mountains to the east, are part of the west-trending Transverse Ranges, which form the northern boundary to the Los Angeles Basin. The mountains form a topographic, geomorphic, geologic, and tectonic barrier in the region.

On its west side, the low-lying beach forms a buffer between the Pacific Ocean and the coastal bluffs. The southern portion of the city is sitting on older marine, lake, playa and estuarine deposits that are now slightly to moderately elevated above the active floodplain of Ballona Creek, located to the south.

Ground surface elevations across the city vary from 0 to 10 feet above mean sea level (amsl) along the beach, to approximately 175 feet amsl at the eastern end of the Santa Monica Airport and 340 to 370 feet amsl near the northeastern corner of the city, on Brentwood Knoll and near the intersection of 26th Street with La Mesa Drive. The coastal bluffs in the northwestern corner of the city rise approximately 50 to 150 feet above the beach below. Farther north, in the Pacific Palisades area, the bluffs are approximately 200 feet high.

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Figure 2-1: Physiographic Map of Santa Monica and Surrounding Areas (physiographic elements in black and white; cities in darker blue; City of Los Angeles neighborhoods in light blue; for a larger version of this map refer to Map H-1 in Appendix H) Major Rivers and Other Bodies of Water
There are no major rivers or floodways extending through or near the city of Santa Monica. Ballona Creek, which flows into the ocean just south of the Marina del Rey area, is now a relatively small, mostly channelized distributary of the Los Angeles River, but in centuries past, this stream used to carry the Los Angeles River floodwaters out to sea through the Ballona Lagoon, a shallow estuary that historically extended north to within 0.5 miles of Santa Monica. The last time this happened was between 1815 and 1825 (for a more in-depth discussion on this topic, see Section 8). Geologic maps and older topographic maps of the region suggest that streams draining the foothills of the Santa Monica Mountains in the area east of Brentwood Knoll converged in what today is the eastcentral portion of Santa Monica and then drained west following the low-lying area now mostly occupied by the I-10 Freeway. Most intermittent drainage in this area is now captured by catch basins and storm drains.

The north end of the city generally coincides with the southern side of the canyon formed by Santa Monica Creek, and near its northwestern end, with the southern portion of Rustic Creek Canyon.

During the last glacial maximum, when sea-level was approximately 300 feet lower than today,

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these creeks incised down to reach equilibrium with the lower sea-level, in the process forming the deeply incised canyons that are there today. Both of these creeks are concrete-lined and have significant flows only following rainstorm events. Flooding in these streams does not impact Santa Monica, except at their mouth, where they debouch at the beach. Here, in the northwestern corner of Santa Monica, FEMA has identified a 100-year flood zone due to storms. The coastal region is within a 100-year flood zone dominated by storm surges.

Santa Monica is downstream of the Stone Canyon dam and reservoir. If the dam failed, the floodwaters could inundate a portion of the city, in the area around Olympic Boulevard and the I-10 Freeway, with significant impacts on the residential and commercial structures in the area, and thus the residents and workers that occupy those buildings. This is also discussed further in Section 8.

Climate
Santa Monica enjoys a Mediterranean-type climate, with typically mild, sunny winters, and warm, dry summers. Its coastal location, however, provides an ameliorating effect, with smaller daily and seasonal ranges in temperature compared to other locations farther inland. Average daily temperatures in the city of Santa Monica range from about 56 to 57 degrees Fahrenheit in the winter months (December to February) to 65 to 69 degrees in the summer months (July through September).

However, the temperatures can vary by more than 17 degrees, as the average minimum and average maximum ranges measured at the Santa Monica Pier (Table 2-1) and the Santa Monica Airport (Table 2-2) weather stations show. Table 2-3 shows that historically, temperatures in Santa Monica have deviated substantially from the average values, with both unseasonally cold and hot temperatures having been measured in the city. Note, however, that most unseasonally cold days were measured in the first 20 years of the 1900s, whereas most of the unseasonally hot days have been measured in the past decade or so.

Table 2-1: Mean Minimum (Min), Average (Ave) and Maximum (Max) Monthly Temperature at the Santa Monica Pier
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
Min 49.6 49.7 51.8 53.2 55.8 59.2 61.5 62.3 60.9 58.5 53.6 49.5 55.5 Ave 55.8 56.0 56.8 58.3 59.6 62.7 65.4 66.0 65.5 63.0 60.3 56.5 60.5 Max 62.0 62.2 61.8 63.4 63.4 66.3 69.4 69.7 70.0 67.5 66.9 63.4 65.5 Monthly climate normal based on data collected at the Santa Monica Pier between 1991 and 2020. From https://www.weather.gov/ accessed May 16, 2024.

Table 2-2: Mean Minimum (Min), Average (Ave) and Maximum (Max) Monthly Temperature at the Santa Monica Municipal Airport
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
Min 48.7 49.0 51.0 52.8 56.6 59.6 62.9 63.2 62.3 58.1 52.0 47.7 55.3 Ave 57.3 57.3 58.7 60.4 62.7 65.5 69.0 69.8 69.2 66.1 61.0 57.0 62.8 Max 66.0 65.6 66.4 68.1 68.9 71.4 75.1 76.5 76.1 74.0 70.1 66.2 70.4 Monthly climate normal based on data collected at the Santa Monica Municipal Airport between 1991 and 2020. From https://www.weather.gov/ accessed May 20, 2024.

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Table 2-3: Record Monthly Temperatures (°F) and Years of Record in Santa Monica Temp Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual High 88
2018
90 2022
94 2015
95 2009
94 2014
92 1957
92 2018
95 1983
103
2010
101
2017
100
1966
89 1979
103
2010
Low 26
1913
32 1903
28 1907
33 1917
39 1915
41 1908
42 1906
47 1919
40 1907
37 1919
32 1919
30 1916
26 1913
Based on data recorded between 1900 and 2023 as follows: 1900-1938, Santa Monica weather station near the intersection of 11th Street and Olympic Boulevard; 1939-2000, Santa Monica Pier; 2001-2023, Santa Monica Municipal Airport.

Source: https://www.extremeweatherwatch.com/cities/santa-monica, with data from the NOAA National Climate Data Center accessed on September 1, 2023.

Rainfall in the Santa Monica area averages around 12 inches per year. The data available suggest that the Santa Monica Pier, on average, receives about 1.7 inches more rain per year than the Santa Monica Airport. However, because the time range covered by the records differs between these two stations, the differences could also be indicative of an overall drier trend. This is presented on Table 2-4. This table also presents data for three different rain stations in Los Angeles (station at the Civic Center, which in 1999 was replaced by the station at USC0F 1 , and a station at LAX). The table also
lists average rainfall totals at the San Gabriel Fire Station that illustrate that areas at higher elevations, above the Los Angeles basin, generally receive noticeably more rainfall. Rainfall averages by month for the Santa Monica area are summarized on Figure 2-2 below, which shows that most precipitation occurs during the winter months between November and March, with very little to no rain measured in June through September.

Table 2-4: Averages of Annual Cumulative Rainfall for Santa Monica (historical and current), Los Angeles (historical and current), and San Gabriel (historical) Weather Station Location and Time Range Cumulative Inches per Year (Averaged)
Santa Monica Pier (1948-2005) 12.87
Santa Monica Airport (1998-2024) 11.19
Los Angeles Civic Center (1950-1995) 14.9
Los Angeles USC (30-year average between 1999-2020) 14.25 Downtown Los Angeles (1844-2024 combined between Civic
Center and USC stations)

14.82 Los Angeles International Airport - LAX (1944-2024) 11.99 San Gabriel Fire Department (1939-1995) 17.46
Sources: https://wrcc.dri.edu/cgi-bin/cliMAIN.pl?casmon, https://www.laalmanac.com/weather/we139a.php, https://www.laalmanac.com/weather/we13.php, https://www.laalmanac.com/weather/we09a.php, https://wrcc.dri.edu/cgi-bin/cliMAIN.pl?casgfd; all accessed July 2, 2024. 1 According to https://www.laalmanac.com/weather/we13.php (accessed on July 2, 2024), on May 20, 2024, the official Downtown Los Angeles weather observation site was relocated from the University of Southern California (USC) campus to the Frank Hotchkin Memorial Training Center in Elysian Park. The new site is approximately four miles northeast of the USC campus, at the training center for the Los Angeles Fire Department, on the south side of Dodger Stadium.

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Figure 2-2: Average Annual Rainfall by Month, Recorded at the Santa Monica Pier Weather Station (historical values) and the Santa Monica Airport (“current normals”) However, “average” precipitation means very little in this region, as annual rainfall amounts have ranged from one-third the normal amount to more than double the normal amount, with rainfall in southern California characterized as “feast or famine.” This is covered in more detail in Section 8.

Soils and Rocks
The sediments and soils underlying Santa Monica determine to some extent the potential geologic hazards that may occur in different regions of the city. Therefore, understanding the geologic characteristics of the sediments underlying Santa Monica is an important first step in hazard mitigation and avoiding at-risk development. The types and characteristics of the unconsolidated sediments, soils, and, at depth, the bedrock, that underlie the city are also a reflection of the geologic and climatic processes that have affected this region in the past several million years.

Although located near the rugged Santa Monica Mountains, the landscape within the city itself is relatively simple (for a geologic map of the area, refer to Figure 9-2, and Plates H-3a and H-3b in Appendix H). The northern portion of the city is underlain by a broad, gently south-sloping alluvial fan that emanated from the mountains to the north. These deposits were transported to their current location by ancestral streams and/or gravity (as mudflows or slopewash) over thousands to tens of thousands of years, building an approximately 80- to 100-foot-thick section of sand, gravelly sand and silt at the base of the mountains. We know that the Santa Monica Mountains are the source for these sediments because the gravels, which occur in large amounts in the alluvial fan deposits, typically consist of clasts of bedrock types that crop out in these mountains. The rock type most

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often seen in the gravelly sections is Santa Monica slate, a dark bluish gray metamorphic rock, but lesser amounts of granitic, volcanic and sedimentary rocks also common in the Santa Monica Mountains are also present. The alluvial surface is now disconnected from the mountains by the deep ravine of Santa Monica Canyon. At depth below the alluvial fan deposits is a thick sequence of non-marine and marine sediments that extend to depths of between 5,000 and 12,000 feet.

On its western boundary, the low-lying beach serves as a buffer between the Pacific Ocean and the coastal bluffs (the Pacific Palisades), with ongoing erosional processes causing the retreat of these bluff faces. The beach areas and the stream channels north and south of the city are filled with historical to latest Holocene (less than about 4,000 years old) deposits. Near the southwestern portion of the city, between Barnard Way on the west, Main Street on the east, and Strand Street on the north, wind-deposited (eolian) deposits have been mapped. All of these youthful sediments are susceptible to differential settlement, liquefaction (if water occurs within about 35 feet of the ground surface), and erosion. Older marine, lake (lacustrine), playa or estuarine deposits, now elevated above the active floodplain, are present in the southern portion of the city. These deposits consist of sand, silty sand and gravel, in some areas cemented by calcite accumulation or modified by soilforming processes. These deposits may be corrosive to metals or concrete, and where capped by soils, may have a high expansion potential. These issues can be mitigated if recognized prior to or during construction.

Other Significant Geologic Features
The city of Santa Monica is located in the western half of southern California, and as a result lies on the Pacific (tectonic) Plate. The Pacific Plate moves northwesterly at a rate of approximately 50 millimeters (2 inches) per year relative to the North American plate, with the San Andreas fault system forming the boundary between plates. The city of Santa Monica is also located near the transition zone between the Transverse Ranges and the Peninsular Ranges physiographic provinces (regions of distinct geology, topography and sometimes ecology). Aligned with the San Andreas fault, the Peninsular Ranges province is represented by a series of northwest-trending faults, mountain ranges and valleys stretching from the base of the Santa Monica Mountains on the north to the Mexican border to the south. The west-trending Santa Monica-Hollywood fault zone, and the Santa Monica Mountains and San Gabriel Mountains to the east, are part of the Transverse Ranges province.

Earthquake faults in this region are mainly of the strike-slip and oblique-slip type, and where they have been most recently active, they have deformed the landscape and altered drainage patterns.

Examples of strike-slip faults in this region include the Palos Verdes, Newport-Inglewood and Elsinore-Whittier faults. The Newport-Inglewood fault zone trends southeasterly across the Los Angeles Basin and is responsible for uplifting the chain of low hills and mesas that extends from Beverly Hills to Newport Beach across the relatively flat coastal plain (including Beverly Hills, Cheviot Hills, Dominguez Hills, Signal Hill, and Newport Mesa). The fault is an active structure and was the source of the 1933 magnitude (M) 6.4 Long Beach earthquake. The Santa Monica fault is considered a left-lateral oblique-slip fault that is in part responsible for uplift of the Santa Monica Mountains. Several traces of this fault have been mapped across the city of Santa Monica. The Santa Monica fault has not caused a significant earthquake in historical times, but is considered seismically active. This is discussed further in Section 6.

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The Los Angeles Basin experiences many small tremors every year, but its history has been shaped by several relatively infrequent, but powerful earthquakes. The first historical earthquake in southern California was recorded in 1769, when the Portolá expedition was camped next to the Santa Ana River in what is now the Olive community in the city of Orange, but earthquakes undoubtedly have shaken the area for millennia. Other more recent earthquakes occurred in 1812, 1857, 1933 (Long Beach), 1987 (Whittier Narrows), 1994 (Northridge), and 2019 (Ridgecrest). The Northridge 1994 earthquake (M 6.7) dramatically affected Santa Monica and is to date the most expensive earthquake in United States history due to its proximity to the Los Angeles area and extensive damage to structures. The earthquake caused a total of 57 deaths, 1,500 injuries, and damaged approximately 12,500 structures, with the city of Santa Monica hit particularly hard.

Given that paleoseismological research indicates that great earthquakes (i.e., M >7.6) occur on the San Andreas fault at intervals between 45 and 332 years, with an average interval of 140 years, another similar earthquake on the San Andreas fault is considered likely in the not-too-distant future (if not already overdue). This fact alone should encourage local governments to strengthen their infrastructure and prepare for “the Big One.” Moreover, as discussed in Section 6, there are other faults closer to Santa Monica, including the Santa Monica fault, that have the potential to cause more damage to the city than the more-distant San Andreas fault. The earthquake hazard to the Los Angeles basin and the cities therein, including the city of Santa Monica, is thus considered severe.

COMMUNITY HISTORY
The first known inhabitants of the Los Angeles Basin, including the Santa Monica area, were Native Americans from the Gabrielino/Tongva (or Tobikhar) nation. Together with the Chumash to the north, in the Santa Barbara region, and the Kymeyaay nation to the south, in what is now San Diego County, these groups occupied a 4,000-square-mile area that extended from the Mojave Desert in the east to the Channel Islands offshore (which they reached with sea-worthy plank-built canoes).

When Spanish explorer Juan Cabrillo sailed past southern California in 1542, the first Europeans to sight the California coastline, the Tongva are thought to have numbered between 5,000 and 10,000 individuals.
1F
2 Intense contact between the Spanish and the Tongva only began more than 200 years later, when the first land expedition by Europeans into what is now Los Angeles County was led by Gaspar de Portolá in 1769. This was followed in 1771 with the founding of the Mission of San Gabriel Arcángel by Junípero Serra. Many Tongva were forcibly relocated to the mission grounds and surrounding areas, generally as enslaved laborers forced to learn the European style of farming and livestock husbandry, to tend to the mission’s orchards, fields and animals. Old World diseases brought by the Spanish led to the rapid collapse of the Tongva people in the late 18th century.

In 1839, the governor of Alta California, Don Juan Bautista Alvarado, awarded a Mexican land grant to Francisco Sepúlveda II, a soldier and citizen of Los Angeles. The 33,000-acre land grant, referred to as Rancho San Vicente y Santa Mónica, included what is today Brentwood, Mandeville Canyon, and parts of Bel Air, West Los Angeles, and Santa Monica. Ownership of these land grants by Spanish 2 Lepowsky, M., 2004, Indian revolts and cargo cults: Ritual violence and revitalization in California and New Guinea, in Harkin, M. E. (editor), Reassessing revitalization movements: Perspectives from North America and the Pacific Island: University of Nebraska Press, Lincoln, NE, pp. 1–61, ISBN 9780803224063.

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families was honored by the 1848 Treaty of Guadalupe Hidalgo following the Mexican-American War. Don Francisco died in 1853, and his heirs sold their San Vicente y Santa Monica property to the American businessman Robert S. Baker in 1872, who bought it to extend his cattle and sheep business holdings in southern California. In 1874, Mr. Baker sold a three-quarter interest to the property to Nevada Senator John Percival Jones, and in April 1875, Mr. Baker married Arcadia Bandini de Stearns, a wealthy California landowner in her own right, and a well-known socialite.

Also in 1875, the Bakers and Senator Jones decided to subdivide a part of the property they jointly owned and create the town of Santa Monica. As part of the process, they filed a Plat map for the first subdivision in Santa Monica. Residential lots 150 feet deep and 50 feet wide were planned between Ocean Avenue on the west, 26th Street on the east, and between Montana Avenue on the north and Colorado Avenue on the south. Arcadia Bandini de Stearns Baker is credited for creating or helping create2F
3 the original map of the city, and in the process designating lots for businesses, schools, churches, and other community structures. The lots set aside for schools and parks she ceded to the city. Stearns Baker also donated the land for Pacific Palisades Park to Santa Monica, and the property where the Veteran’s Administration is located. The City of Santa Monica was incorporated in 1886, and became a sea-side resort, with railway connection between the Los Angeles area and Santa Monica provided by the Pacific Electric Railway. Hotels, bathhouses and amusement piers catered to the beachgoers and provided employment opportunities.

In 1922, Donald Will Douglas Sr. built a plant in Santa Monica establishing the Douglas Aircraft Company. The factory provided jobs and in 1924 placed the region on the world map when two of four Douglas-built planes landed on the field after flying more than 27,500 miles in 175 days, as part of their effort to circumnavigate the globe.
3F
4 Population in the Santa Monica area more than
doubled during this period, from 15,252 in 1920 to 37,146 in 1930. During the Great Depression (1929-1939), however, Santa Monica’s businesses, especially those in the hospitality industry, suffered greatly, with many going bankrupt. A positive that came out of that period is that several important buildings in Santa Monica were built with funding provided by the Work Projects Administration (WPA), part of Franklin D. Roosevelt’s New Deal program to provide jobs to millions of unemployed people, mostly building public works and infrastructure projects. Several buildings in Santa Monica were built with WPA funds including Santa Monica City Hall. Population between 1930 and 1940 increased by 44%, to about 53,500 residents.

Employment prospects in the region improved when the United States declared war during World War II. Military personnel and defense workers arrived in southern California to fill the logistical needs created by the war effort. In Santa Monica, the Douglas Aircraft Company was commissioned to build aircraft for various branches of the U.S military. By 1943, reportedly more than 44,000 people were employed by the company. The population in the region increased dramatically, and residential developments and shopping centers sprung throughout the Los Angeles region; within a few decades, the Los Angeles Basin was virtually built out. In Santa Monica, population between 1940 and 1950 increased nearly 34%, with nearly 71,600 residents reported in 1950. Immediately after the war, construction began on the freeway system, and the face of southern California was forever changed. Although Santa Monica’s population increased further between the 1950s and the 1970s (83,249 residents in 1960 and 88,289 residents in 1970), some residential communities in the city were uprooted by construction projects, including the Santa Monica Civic Auditorium, 3 https://en.wikipedia.org/wiki/Arcadia_Bandini_de_Stearns_Baker and https://smmirror.com/2010/11/arcadiabandini-santa-monica-shaper-hometown-hero/m, both accessed in July 2024. 4 https://en.wikipedia.org/wiki/Santa_Monica,_California, accessed on July 23, 2024.

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completed in 1958, and the Santa Monica Freeway, completed in 1966. The Civic Auditorium was built where Belmar Triangle, the first African American neighborhood in the city used to be located.

The freeway project impacted the Pico neighborhood, another significant African American community4F
5 , and home also to Latinos, as well as low-income residents. Many properties were seized under eminent domain laws.
5F
6 Both projects resulted in the displacement of hundreds of families of color and in 2021 the City of Santa Monica officially apologized for targeting these neighborhoods for condemnation.

Today, Santa Monica is home to many businesses in a wide variety of industries, including technology, digital media and content, television and film, banking, real-estate, apparel, music, gaming, fitness, food, entertainment and hospitality. The City is also home to Santa Monica College and two hospitals (UCLA Santa Monica Medical Center and Providence Saint John’s Health Center); combined, these institutions provide thousands of jobs. To support its residential and commercial bases, the City has three main shopping districts, in addition to hundreds of boutiques, restaurants and small businesses.

POPULATION AND DEMOGRAPHICS
The city’s small area and existing housing stock largely control the number of people that can call Santa Monica home. As a result, population counts for Santa Monica have not varied significantly between 1970 and 2020 (Table 2-5). According to U.S. Census data, population remained fairly stable between 1970 and 2010, and in fact decreased by 4,230 people between 1980 and 2000.

While some population growth occurred after 2000, with an increase of 6.7% between 2000 and 2010 and 3.7% between 2010 and 2020, population estimates for 2023 indicate that the city’s population has since slightly decreased. Nevertheless, Santa Monica is one of the most densely populated cities in California, and in the United States as a whole, with around 10,800 people per square mile (still considerably shy of the 74,870 people per square mile in Manhattan, New York, according to the 2010 Census).

Table 2-5: Historical Population Counts for the City of Santa Monica Year Population
1970 88,289
1980 88,314
1990 86,905
2000 84,084
2010 89,736
2020 93,706
2023 (estimated) 89,922
Source: United States Census Bureau Decennial Census of Population and Housing (https://data.census.gov/, accessed June 1, 2024).

Santa Monica’s generally consistent population counts over the past 50 years are most likely the result of limited housing development (which is constrained by the city’s geography and the fact that it is already densely built up). For example, while in California there has been a 13.9% increase in 5 Ibid.
6 https://www.kcrw.com/news/shows/greater-la/toxins-santa-ana-edu/santa-monica-displaced-black-familieshousing, accessed July 24, 2024.

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occupied housing units between 2000 and 2020, Santa Monica has only experienced a 2.7% increase in housing stock during the same period. Families in Santa Monica are, on average, smaller, with 2.82 members compared to the State’s average family size of 3.39. The average household size in Santa Monica has slightly increased in the past two decades, from 1.84 in 2000 to 1.95 in 2020, while the State-wide average has remained stable, at 2.87 in 2000 and 2.89 in 2020. According to the Santa Monica Housing Element Needs Assessment, the City’s housing stock grew by 1,717 units between 2010 and 2020, while population during that same time period grew by 2,621 individuals.

This suggests that Santa Monica’s slight increase in population during that time period was accommodated by slight increases in both household size and number of housing units. In 2020, the City’s housing stock consisted of approximately 52,629 total units, 11,572 (22%) of which were single units, and 40,853 (78%) which were multi-units.

Densely populated areas pose a special challenge because of the large number of people potentially exposed to a natural hazard event, such as an earthquake, at the same time. Essentially, high population densities increase risk. Furthermore, high-density housing increases the chances of structure fires spreading from one building to the next, especially in older structures. Narrow residential streets and narrow passageways between buildings can also make it more difficult for emergency response vehicles and personnel to reach those in need, and the high ratio of residents to emergency responders can affect response times.

History shows that the impacts of natural hazards in terms of exposure, vulnerability and the ability to recover vary greatly among different segments of the population. Disasters pose particular risk to older populations6F
7 and children, women, racial and ethnic minorities (especially indigenous and African American people in the United States), disabled people, and low-income populations. 7F
8 For
example, an analysis of flooding in Houston, Texas after Hurricane Harvey (2017) demonstrated greater flooding extent in neighborhoods with higher proportions of Black and socioeconomically deprived people8F
9 , highlighting inequities to exposure. Another example comes from Christchurch, New Zealand and the fatal Canterbury earthquake sequence that occurred between 2010 and 2011.

Efforts to rebuild the city have been slow and unequal, especially impacting low-income residents and renters. Despite a third of Christchurch’s population being renters, rebuilding housing infrastructure has not been prioritized, causing dramatic rent increases. Instead of focusing on multihousehold structures, there is a perceived priority of the local government in rebuilding higher income parts of the city first.9F
10 Addressing inequities and being proactive about mitigating disasters is known as environmental justice. Specifically, the Environmental Protection Agency (EPA) defines environmental justice as the 7 Being older than 60 was the "single most important factor in determining who died in Hurricane Katrina" (Peek, L., 2013, Peek, Lori., Age; in Thomas, D.S.K., Phillips, B.D., Lovekamp, W.E., and Fothergill, A. (editors), Social Vulnerability to Disasters, 2nd Edition: CRC Press, Boca Raton, FL, pp. 167-198. 8 Ryder, S.S., 2017, A Bridge to Challenging Environmental Inequality: Intersectionality, Environmental Justice, and Disaster Vulnerability: Social Thought & Research, Vol. 34, pp. 85-115; available at https://www.jstor.org/stable/44807699. 9 Chakraborty, J. et al., 2019, Exploring the Environmental Justice Implications of Hurricane Harvey Flooding in Greater Houston, Texas: American Journal of Public Health, Vol. 109, No. 2, pp. 244-250; DOI:

10.2105/AJPH.2018.304846. 10 Sovacool, B.K., Tan-Mullins, M., and Abrahamse, W., 2018, Bloated bodies and broken bricks: Power, ecology, and inequality in the political economy of natural disaster recovery: World Development, Vol. 110, pp. 243-255; https://doi.org/10.1016/j.worlddev.2018.05.028.

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“just treatment and meaningful involvement of all people, regardless of income, race, color, national origin, Tribal affiliation, or disability, in agency decision-making and other Federal activities that affect human health and the environment.”
10F
11 Discussions about natural hazards that include local citizen groups, insurance companies, and other public and private sector organizations, including small-business owners and residents, can help ensure that all members of the community are part of the decision-making processes.

As the paragraphs and tables below illustrate, Santa Monica’s residents include a large proportion of single-adult households, including especially women-led households, older people, disabled people, and minorities. All of these groups have the potential to be significantly impacted by a natural disaster. Furthermore, a very large proportion of Santa Monica’s residents rent rather than own the buildings that they live in. Renters and landlords are generally less likely to take on mitigation actions that will make their structures more hazard resistant. Furthermore, landlords are typically not eligible for FEMA funding following a disaster, a situation that can significantly delay the repair of rental units so that they can be re-occupied. All of these conditions can hinder the processes of disaster preparedness and recovery, unless a concerted effort is made to educate the entire population on the hazards likely to impact the community, and on mitigation actions that can be implemented by individual households and small businesses to reduce the impacts from these hazards. Renters in particular, should be aware that FEMA typically does offer limited help to eligible renters impacted by a disaster in the form of free referral services to find alternate housing, and in some instances, money to rent a different place to live for a limited period of time.

The U.S. Census Community Survey for Santa Monica in 2022 shows that a large proportion of households in the city are headed by women.
11F
12 Specifically, 37.5% of households are occupied by
women with no spouse present, compared to 20.0% of households occupied by men with no spouse present, and 33.9% of households being occupied by married couples. These statistics differ greatly from those for the entire state. In California, nearly half (48.1%) of households are occupied by married couples, 26.2% are occupied by female householders, and 18.0% are occupied by male householders.

Santa Monica has a relatively older population than California. The median age in Santa Monica is

43.3 years, which is around 5 years older than the median age for the State (37.9 years). Figure 2-3 shows the estimated age distribution for Santa Monica’s residents based on the 2018-2022 American Community Survey 5-Year Estimates data. Compared to State averages, households in Santa Monica include fewer children and young adults. There is a spike in the population of people in their late twenties and thirties, and in general Santa Monica has a high proportion of elderly people: 21.1% of people in Santa Monica are 65 years and older, compared to 15.8% in the State as a whole.

As the data presented in Tables 2-5 and 2-6 show, almost a quarter (22.6%) of Santa Monica’s population is foreign born. Of the foreign-born population in the city, 61.8% are naturalized U.S. citizens and thus 38.2% are not U.S. citizens. Of all foreign-born residents in Santa Monica, 37.3% originate from Asia, 27.4% originate from Europe, 23.9% originate from Latin America, and the 11 https://www.epa.gov/environmentaljustice 12 The person designated as the householder is the “reference person” to whom the relationship of all other household members, if any, is recorded. Typically, women-headed households are households where either no adult men are present, due to divorce, separation, migration, non-marriage or widowhood; or where men, although present, do not contribute to the household income because of illness, disability, old age or other similar situation.

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remaining 11.4% originate from other regions. Relatedly, English is the primary language spoken in Santa Monica, with 72.2% of residents speaking only English, compared to the State average of

56.1%. The second most common language in Santa Monica is Spanish, which 11.1% of residents speak as their primary language. This is important to consider and plan for in hazard reduction, emergency preparedness, and mitigation actions: all emergency and disaster preparedness communications should be sent out in both English and Spanish to reach the largest possible percentage of the city’s population.

Figure 2-3: Age Distribution of the Population in Santa Monica Compared to California Source: United States Census Bureau American Community Survey, 2018-2022 (https://data.census.gov/, accessed June 3, 2024)
Table 2-6: Place of Birth Statistics for Santa Monica Residents Compared with California (2020 American Community Survey)
Santa Monica California
Born in United States 77.4% 73.4%
Born in California 39.0% 56.0%
Born in Different State 36.1% 16.0%
Born in Puerto Rico, U.S. Islands, or Abroad, to American Parents 2.3% 1.4% Foreign Born 22.6% 26.6%

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Table 2-7: Population Breakdown, by Race, in the City of Santa Monica (2020) Race % of Santa Monica’s Population
American Indian / Alaska Native 0.7
Asian 8.8
Black or African American 5.3
Native Hawaiian or Other Pacific Native 0.1
White 69.0
Some other race 4.0
Two or more races 12.1
Population by Hispanic or Latino Origin (of any race)
Persons of Hispanic or Latino origin 17.2%
Persons not of Hispanic or Latino origin 82.8%
According to the U.S. Census data, the median household income (2018-2022) in Santa Monica was $106,797 (compared to $91,905 in California and $75,149 in the entire United States). The poverty threshold varies depending on household make-up, the number persons in the household and number of children. The percentage of individuals living in poverty in the city of Santa Monica is 10.1%, which is lower than the California rate of 12.6%. On average, Santa Monica families have lower rates of poverty than California. However, as shown in Table 2-7, families with female householders and children under 5 years old, and people over 65 years old are at particular risk of poverty in Santa Monica. Specifically, for 2018-2022, 33% of the households in Santa Monica headed by women with no partner present and with related children less than 5 years old were deemed to be below the poverty level. This amounts to approximately 203 families. In the same time period, about 17.3% of the seniors more than 65 years old in Santa Monica were considered to be living below the poverty level, compared to 11.0% of the seniors in all of California.

Table 2-8: Percentage of Families and People in Santa Monica and California whose Income in the Prior 12 Months Was Below Poverty Levels (2018-2022, 5-Year Estimates) Santa Monica California
All Families 6.7% 8.5%
With related children under 18 years 7.5% 12.5%
With related children under 5 years 6.7% 9.7%
Married Couple Families 5.1% 5.1%
With related children under 18 years 4.6% 6.7%
With related children under 5 years 3.4% 4.3%
Families with Female Householder, no spouse present 12.9% 20.3% With related children under 18 years 13.6% 29.2%
With related children under 5 years 33.0% 30.3%
All People 11.6% 12.1%
Under 18 years 6.8% 16.8%
65 years and over 17.3% 11.0%
Source: Selected Characteristics of People at Specified Levels of Poverty in the Past 12 Months, using the 2022 American Community Survey 5-Year Estimates Subject Tables, from data.census.gov. Note that the census tables provide margins of error; those are not included above for simplicity purposes.

Santa Monica’s population has slightly higher disability rates compared to the California average.

According to the 2022 1-Year American Community Survey, 12.3% of people in Santa Monica are disabled, compared to 11.7% in California. Ambulatory difficulties are the most common disability,

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affecting 7.8% of Santa Monica residents, whereas 6.3% of Santa Monica residents have supported living needs and 5.8% have cognitive disabilities. Disabled populations are at high risk during natural hazards, especially those with mobility issues. It should therefore be a priority to have contingency plans and support systems for these people during such emergencies.

Examining the reach of hazard mitigation policies to special needs populations may assist in increasing access to services and programs. FEMA's Office of Equal Rights addresses this need by suggesting that agencies and organizations planning for natural disasters identify special needs populations, make recovery centers more accessible, and review practices and procedures to remedy discrimination in relief application or assistance.

HOUSING AND COMMUNITY DEVELOPMENT
As mentioned in the introduction, the city of Santa Monica is built out; there are only a few vacant parcels and a few lots with large backyards that could be re-developed into higher-density buildings.

Therefore, in the last few years there has been little development (see Table 2-8). This also means that structures in Santa Monica tend to be older: over 75% of the housing structures in Santa Monica were built more than 40 years ago. This poses concerns for the integrity of these structures, especially in response to natural disasters.

Thus, a large regional earthquake has the potential to result in a large percentage of Santa Monica households and residents to be displaced, in numbers likely to be too large for the City to respond to effectively (see Section 6). Displaced households may need alternative short-term shelter, provided by family, friends, temporary rentals, or public shelters established by the City, County or by relief organizations such as the American Red Cross. Long-term alternative housing may require import of mobile homes, net emigration from the impacted area, and/or, the eventual repair or reconstruction of new public and private housing. Given that a large percentage of the housing units in Santa Monica are rental properties (see Table 2-9), a damaging natural hazard event has the potential to not only significantly impact Santa Monica’s residents, but the City’s makeup, as many residents may choose to find alternate housing elsewhere, in other cities. The number of people seeking short-term public shelter is of most concern to emergency response organizations. The longer-term impacts on the housing stock are of great concern to local governments, such as cities and counties.

Table 2-9: Year Housing Structures in Santa Monica Were Built (and Comparison with California) Year Housing Structure was Built Santa Monica,
Total Number, (Percent of Total)
California,
Percent of Total
2014 or later 847, (1.9%) 2.2%
2010 to 2013 678, (1.5%) 1.8%
2000 to 2009 2,319, (5.1%) 10.9%
1980 to 1999 6,824, (14.9%) 26.1%
1960 to 1979 17,483, (38.3%) 30.8%
1940 to 1959 11,094, (24.3%) 19.3%
1939 or earlier 6,461, (14.1%) 8.9%
Source: U.S. Census Bureau, Selected Housing Characteristics, 2018-2022 American Community Survey 5-Year Estimates, accessed on June 5, 2024.

Total Estimated Housing Units in California: 13,103,114; Total Estimated Housing Units in Santa Monica: 45,706

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Housing stock is in many direct and indirect ways one of the most important commodities in a city.

As mentioned above, if a natural disaster, such as an earthquake, damages several houses in the city, this has a significant impact not only on the residents of those structures, but on the City itself.

An extreme, but real, example of this is New Orleans following Hurricane Katrina. After this catastrophic event, New Orleans lost more than half of its population due to permanent relocation and more than two years later entire neighborhoods were vacant, the houses still in ruins. Many past residents of these communities started new lives in other cities and states and have not come back.

In 2020, there were still around 100,000 fewer people in New Orleans than in 2005, substantially diminishing New Orleans’ tax base. New Orleans is rebuilding and recovering, but it has taken time.

Many Santa Monica residents live in apartments or condominiums that have multiple units per structure (Table 2-9). In fact, a little less than 50% of Santa Monica residents live in structures with 10 or more units, compared to the state average of 17.4%. Similarly, only 18.4% of Santa Monica residents live in a detached one-unit house, while the California average is much higher at 58.3%.

As discussed previously, living in close quarters can put people at increased risk during some disasters or emergencies, such as structural fires that can spread from one housing unit to another, and congested exits. Structures with multiple stories can pose risks if elevators stop functioning or stairways get blocked. Mitigation measures that can be undertaken by households to protect themselves from the impacts of some of these disasters are discussed in each appropriate section of this report.

Table 2-10: Selected Housing Characteristics in Santa Monica and California Santa Monica California
Total Housing Units 52,389 14,277,867
Occupied housing units 44,495 (84.9%) 13,072,122 (91.6%) Vacant housing units 7,894 (15.1%) 1,205,745 (8.4%)
Owner-occupied 27.9% 55.3%
Renter-occupied 72.1% 44.7%
Home-ownership rate 31.8% 55.8%
Units in Structure
1-unit, detached 8,414 (18.4%) 58.3%
1-unit, attached 1,780 (3.9%) 7.2%
2 units 622 (1.4%) 2.3%
3 or 4 units 3,922 (8.6%) 5.4%
5 to 9 units 10,235 (22.4%) 5.9%
10 or more 20,658 (45.2%) 17.4%
Mobile homes 75 (0.2%) 3.5%
Housing Statistics
Average household size 1.97 2.94
Rate of single-person households 46.9% 23.8%
Median value of owner-occupied units $1,507,400 $557,100 Median monthly rent / Monthly housing costs for
renter-occupied units $1,900 $1,586
Source: U.S. Census Bureau, Selected Housing Characteristics, 2018-2022 American Community Survey 5-Year Estimates, accessed on June 5, 2024.

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Santa Monica’s residents are well educated. Of the population aged 25 years and older, only 3.9% did not complete high-school, and 7.6% only completed high-school but did not go to college. 22% of this age group completed some college or obtained an associates’ degree, whereas 66.5% completed college, with 30.4% having completed graduate school or obtained a professional degree. This is reflected in the occupations and industries that Santa Monica workers are most commonly engaged in, with 68.5% of the work force involved in management, business, science or the arts (see Table 2-10). Of the city’s population 16 years old and over, an estimated 70.1% participate in the labor force, with an employment to population ratio of about 66.6%. These numbers are higher than for California overall, where the labor force participation for the same age group is estimated at 63.9%, with an employment to population ratio of 60%.

Table 2-11: Employment and Industry in Santa Monica Compared to California Principal Employment Activities Santa Monica California Management, Business, Science, and Arts occupations 68.3% 40.3% Service occupations 10.3% 18.1%
Sales and Office occupations 16.4% 20.9%
Natural resources, Construction, and Maintenance occupations 2.1% 8.8% Production, Transportation, and Material moving occupations 3.0% 11.9% Major Industries
Manufacturing 3.8% 9.0%
Retail trade 6.9% 10.4%
Educational services, and Health care and Social assistance 20.5% 21.2% Transportation, and Warehousing and Utilities 2.3% 4.7% Arts, Entertainment and Recreation, and Accommodation and Food Services 11.3% 10.2%
Professional, Scientific, and Management, and Administrative and Waste Management 25.3% 13.8%
Source: U.S. Census Bureau, 2018-2022 American Community Survey 5-Year Estimates, accessed on June 5, 2024.

TRANSPORTATION, COMMUTING PATTERNS AND ESSENTIAL SERVICES A moderate to large percentage of Santa Monica residents either work in the city, or close to it.

Specifically, 34.6% of Santa Monica’s residents work in the city, with 9.3% working from home (based on data from the ACS 5-Year estimates for 2018-2022). The State average for people working from home is 6%. Southern Californian’s love for their private automobiles is well known, with automobiles being the historically dominant means of transportation in the region. This is true of Santa Monica also, with 63.3% of the city’s residents in the workforce commuting alone via car, truck or van (according to the ACS 5-year estimates for 2018-2022). This percentage is lower than the State average of 72.5%, however. The census data also indicate that 5.1% of Santa Monica residents in the labor force carpool to work, compared to 10.0% statewide. Public transportation is used by 3.6% of the Santa Monica labor force, and another 6.5% walk to work (compared to 4.6 and 2.2%, respectively, for California overall). Additionally, 3.4% of Santa Monica residents bike to work, compared to only 0.8% for the State average.

Of the 65.4% of Santa Monica residents that commute to work outside the city, 63.7% commute less than 30 minutes, and 31.6% commute between 30 and 59 minutes. Only 4.7% of residents that work have a commute longer than one hour. The mean travel time to work (commute) for Santa

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Monica residents is 24.6 minutes. The mean travel time for commuters in California is estimated at

30.2 minutes.

Although the preferred and most common means of transportation in southern California is by automobile, Santa Monica can also be accessed from downtown Los Angeles (LA) by train and bus.

Bus service within the city is provided by Santa Monica’s own Big Blue Bus, and connections to LA are provided by the Los Angeles County’s Metro. The Big Blue Bus is operated by the City of Santa Monica’s Department of Transportation, governed by the Santa Monica City Council and services more than 58 square miles of the Los Angeles metropolitan region. Rides cost $1.10 (as of 2024) for a one-way trip with free transfers within a 2-hour time limit.

The Metro provides several bus lines between Santa Monica and the LA area as follows: Line 4 bus travels between Downtown LA. and Santa Monica via Santa Monica Boulevard, Line 20 travels between Downtown LA and Westwood/Santa Monica via Wilshire Boulevard, Line 33 travels between Downtown LA and Santa Monica via Venice Boulevard, Line 134 travels between the Downtown Santa Monica Station and Malibu, and Line 720 travels between Santa Monica and Downtown LA via Wilshire Boulevard. Santa Monica residents can also travel between Downtown Santa Monica and Downtown LA using the Metro Expo Light Rail Line train (E Line). The Metro Expo Light Rail Line connects the downtowns of both cities, with the most westerly station in Santa Monica located on the corner of Fourth Street and Colorado Avenue. Metro fares cost $1.75 for a one-way ride (as of 2024).

In terms of commuting patterns, the city is bisected by the western terminus of the Interstate 10 (I-10) Freeway, and can be accessed from the east by several major roads including, from north to south, San Vicente Boulevard, Montana Avenue, Wilshire Boulevard, Santa Monica Boulevard, Olympic Boulevard, Pico Boulevard, and Ocean Park Boulevard. Pacific Coast Highway (PCH) connects the western portion of the city with Malibu and other communities to the north, and to Venice, Marina del Rey, Playa Vista, and other communities to the south (Figure 2-4). Most streets in the city are oriented in a northeast to southwest, and northwest to southeast grid, with a few winding roads present locally in areas with topographic relief (Figure 2-4).

Within the city itself, residents and visitors can bike and walk. Santa Monica has an extensive system of bike-designated lanes and most streets also have sidewalks, typically tree-shaded, for pedestrian use. Several shared mobility companies service the Santa Monica region, with bikes, electric bikes and electric scooters available for rental through the providers’ websites or mobile apps.

Several of the hazards discussed in this document have the potential to disrupt automobile traffic and shut down the local and regional transit systems. For example, an earthquake could damage the freeway overpasses so that they are unsafe to cross. Localized urban flooding occasionally impacts sections of the I-10 freeway, the McClure Tunnel, and PCH. Earthquake- and/or storm-induced slope failures can render sections of these roads temporarily unpassable. Even strong Santa Ana winds can make driving hazardous, especially for high-profile vehicles such as trailer trucks.

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Figure 2-4: Major Roads In and Near Santa Monica
(for a larger, scaled-version of this map refer to Map H-2 in Appendix H) In terms of essential services, the City has its own Police and Fire Departments. The Police Department provides traffic control, law enforcement, domestic violence, drug abuse and youth services, among others, for the City and its residents. Information on the Police Department, including contact information, can be obtained here. The Santa Monica Fire Department has five stations across the city and provides full-time services such as fire-fighting, paramedics, fire prevention, search and rescue, hazardous material response, and airport firefighting. Information on the fire hazards in Santa Monica is discussed in Section 10. The City’s Public Works Department provides essential services to the Santa Monica community that include water supply production, treatment, and collection; collection and proper management of recoverable materials; tree trimming and street maintenance. Public education services for the school-aged children in the city of Santa Monica are provided by the Santa Monica–Malibu Unified School District.

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SECTION 3: RISK ASSESSMENT
WHAT IS A RISK ASSESSMENT?
Risk assessment is the process of estimating or calculating the potential losses (in terms of life, injuries, and property and economic damage) resulting from a hazard event. To conduct this analysis, it is necessary to identify and understand the hazards that can impact the community (hazard identification and hazard profiling), assess the vulnerability of the people, buildings and infrastructure that can be impacted by each hazard identified (vulnerability assessment and asset inventory), and estimate the potential losses (risk analysis). Each of these tasks or steps in the process, as it pertains to the city of Santa Monica, is described further below:

Hazard Identification
This is the description of the geographic extent, potential intensity and the probability of occurrence of a given hazard. To assess the perceived impact that various hazards can have on the city of Santa Monica, Resilience Planning Committee members were asked at the kick-off meeting to fill in a spreadsheet provided to them that listed a variety of natural and human-made hazards. A copy of the unfilled hazards matrix is included here as Table 3-1. Individuals were asked to weigh in on (1) the geographic extent of the hazard (widespread, moderate, or small), (2) whether or not, to their knowledge, the hazard has previously impacted the city of Santa Monica, (3) the probability (high, medium, low) of the hazard occurring in the Santa Monica area; and (4) the potential risk (high, medium, low) that each hazard poses to Santa Monica and its residents. Respondents were also encouraged to add other hazards to the list as they saw fit.

The 18 filled-in spreadsheets were collected and the data provided therein were compiled and weighted to develop a score for each hazard based on the answers provided. Points assigned to each hazard were calculated by summing the geographic extent, probability of occurrence and potential risk, as follows: widespread geographic extent, high probability of occurrence and high potential risk were each assigned 3 points; moderate geographic extent, medium probability of occurrence and medium potential risk were each assigned 2 points; and small geographic extent, low probability of occurrence and low potential risk were each assigned 1 point. The number of points earned by each hazard were summed together and the total was then divided by 18, the total number of respondents. If all respondents had identified a hazard as having a widespread geographic extent, high probability of occurrence and posing a high risk to the community, that hazard would have the maximum possible score of 9. Note, however, that some individuals did not assign a value to all hazards, and in a few instances, individual respondents assigned more than one value (such as moderate and small geographic extent) to the same hazard; as a result, not all row groups add to 18.

The final scores for each hazard were ranked from highest to lowest, with the hazard receiving the highest score assigned a rank of 1. The results of this analysis are shown in Table 3-2.

Based on these results, the top-ten ranked hazards in the city of Santa Monica, listed from highest (1) to lowest (10) are: earthquake-induced ground shaking, sea-level rise, Santa Ana winds, high to excessive heat, drought, coastal flooding, surface rupture or surface fault deformation, tsunami, thunderstorms, and liquefaction. These hazards are identified in Table 3-2 with their assigned ranks shown in red text.

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Table 3-1: Blank Spreadsheet Listing Hazards with the Potential to Impact the City of Santa Monica

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Table 3-2: List of Hazards Identified as Likely to Impact the City of Santa Monica, Compiled and Ranked

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Based on input received at the kick-off meeting, and research conducted for this and previous versions of this Plan, the city of Santa Monica can be impacted by several natural hazards, including:
1) earthquakes (and secondary hazards triggered by earthquakes, such as surface fault rupture, liquefaction, slope failures, releases of hazardous materials, after-earthquake fires, and dam and water reservoir failures);
2) tsunamis caused by both near-source and long-distance earthquake sources; 3) storm flooding resulting both from coastal and pluvial processes; 4) slope failures;
5) fires, including urban (structure) fires, wildland fires, and after-earthquake fires; and 6) strong windstorms and severe weather, especially hazards exacerbated by climate change (such as sea-level rise, extreme heat events, drought, and hurricanes).

Human-related hazards that can also impact the Santa Monica area include:
7) non-earthquake related releases of hazardous materials; 8) aviation accidents and other airport-related hazards such as noise pollution; 9) terrorist acts (including active shooters, cyberattacks on infrastructure, releases of harmful chemical or biological agents);
10) acts of civil unrest (protests and mobs); and
11) pandemics.

At this time, and for this document, the City chose to address only the natural hazards identified in items 1 through 6 above, and the risks posed by the human-caused releases of hazardous materials and aviation hazards (items 7 and 8). These were the natural and human-caused hazards deemed to have the greatest potential to cause damage, in terms of casualties and losses, in Santa Monica.

These are also the hazards highlighted in the recently completed and approved Safety Element of the General Plan, a companion document to the Local Hazard Mitigation Plan.

The decision to not include items 9 through 11 from the list above was also informed by City staff indicating that in the past decade a variety of response plans specific to addressing terrorist acts, civil unrest, and pandemics have been developed and are available for City agencies and staff to implement as needed should the need arise. When work on this 2025 update to the Local Hazard Mitigation Plan began, the United States had just recently declared the end of the COVID-19 pandemic, and the City of Santa Monica, like most communities, had extensive experience in the implementation of the pandemic playbooks developed to respond to this crisis. Thus, for example, the COVID-19 playbook developed by the California Department of Public Health provided detailed strategies specific to various sectors of the work force and other populations, including farm and construction workers, school children, Native Americans, immigrants, and the LGBTQ+ community.

Given this recent past experience and the wealth of available resources that can be tailored as needed should a new pandemic impact the region, the City of Santa Monica chose to not include pandemics in the list of hazards addressed here. Some of these hazards, such as cybersecurity threats to critical facilities and pandemics may be addressed in future versions of the Plan.

Each of the hazards selected to be addressed in this 2025 Plan is described in detail in the following sections. Where possible, the geographic extent of each of the identified hazards in Santa Monica is displayed on a map of Santa Monica, although several of the hazards have a regional extent that exceeds the boundaries of the city. The maps that show the estimated geographic reach of these

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hazards are an important element of this document, and are thus included within the section that describes the hazard being considered (e.g., maps of regional and local faults, expected ground accelerations, and zones susceptible to liquefaction or earthquake-induced slope failure are included in Section 6: Earthquake Hazards). Some of the city-specific hazard maps are also presented together in Appendix H in 11x17 format (see list of maps in Table 3-3 below).

Profiling Hazard Events
This process describes the causes and characteristics of each hazard, how each specific hazard has affected the southern California area and the city of Santa Monica in the past, and what parts of Santa Monica's population, infrastructure, and environment have historically been vulnerable to each specific hazard. A profile of each hazard discussed in this Plan is provided in Sections 6 through

13. Therefore, for a description of the history of hazard-specific events, please see the appropriate hazard section.

Table 3-3: List of Maps that are Part of This Plan (Plates are in Appendix H) Figure / Plate Map Title Section of
the Plan
1-1 City of Santa Monica (with dark blue lines showing City boundaries) Section 1
2-1, 9-1 /
H-1 Physiographic Map of Santa Monica and Surrounding Areas Section 2Section 9 2-4 / H-2 Major Roads In and Near Santa Monica Section 2 3-1 / H-3 Critical Facilities In and Near Santa Monica, California Section 3 6-1 Regional Map Showing Select Faults, Physiographic Provinces and Landforms Mentioned in the Text Section 6
6-2 Earthquake Shaking Levels Anticipated in California Section 6 6-4 Notable Regional Earthquakes Section 6
6-5 ShakeMap for a Magnitude 7.4 Earthquake Scenario on the Malibu Coast-Santa Monica-Hollywood Fault System Section 6 6-6 ShakeMap for a Magnitude 7.2 Earthquake Scenario on the Newport-Inglewood Fault Section 6
6-7 ShakeMap for a Magnitude 7.5 Earthquake Scenario on the Compton Thrust Fault Section 6
6-8 Scenario for a M7.1 Earthquake on the Puente Hills Fault Showing Estimated Intensity Values in the Region Resulting from this Event Section 6 6-9 Estimated Percent Building Losses as a Result of a Mw 7.5 Earthquake on the Puente Hills Thrust Fault Section 6
6-10 ShakeMap for a Magnitude 7.8 Earthquake Scenario on the San Andreas Fault (Repeat of the 1857 Fort Tejon Earthquake) Section 6 6-11 ShakeMap for a Magnitude 7.8 Earthquake Scenario (Shakeout) on the Southern San Andreas Fault Section 6
6-12 Faults Mapped and Inferred Through, Near and Below Santa Monica Section 6
6-13 / H-4 Earthquake Fault Zones of Required Investigation In and Near Santa Monica, California Section 6
6-14 / H-5 Seismic Hazard Zones Map, Santa Monica, California Section 6 6-15 / H-6 Census Tracts used in the HazUS Analyses Section 6 6-16 / H-7 Total Residential Building Related Losses as a Percentage of Total Residential Exposure Section 6

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Figure / Plate Map Title Section of
the Plan
6-17 / H-8 Total Commercial Building Related Losses as a Percentage of Total Commercial Building Exposure Section 6
7-1
Bathymetric Map of Santa Monica Bay Showing Continental Slope and Offshore Canyons that Could be Source or TsunamiGenerating LandslidesSection 7 7-3
World Map Showing Approximate Location of Ring of Fire, Subduction Trenches, Active Volcanoes, and Large Earthquakes Between 1900 and 2013
Section 7
7-4 / H-9 Tsunami Hazards Map, Santa Monica, California Section 7 8-2 / H-10 Flood Hazards Map, Santa Monica, California Section 8 8-3 / H-11 Dam Inundation Map, Santa Monica, California Section 8 8-4 / H-12 Anticipated Damage in Santa Monica as a Result of a Stone Canyon Dam Failure Scenario Section 8
9-1 / H-1 Physiographic Map of Santa Monica and Surrounding Areas Section 9 9-2 / H-13a & H13bGeologic Map of Santa Monica and Vicinity (H-13a) with Unit Descriptions (H-13b) Section 9
9-3 / H-1 Bathymetric Map of Santa Monica Bay Showing Offshore Canyons Section 9 9-4 / H-14 Slope Distribution Map for Santa Monica and Adjoining Areas Section 9 9-5 / H-15 Areas in Santa Monica Susceptible to Slope Failure Section 9 10-1 / H-16 Historical (1930-2025) Wildfires Near Santa Monica Section 10 10-2 / H-17 Fire Hazard Zones in and Near Santa Monica Section 10 11-7 / H-18 Flood Extent Along the Santa Monica Coastline Through the Year 2100 Using Three Sea-Level Rise Scenarios Section 11
12-2 / H-19 Hazardous Materials Site Map, Santa Monica, California Section 12 13-1 Airport Location Map Section 13
13-2 Land Use Around Santa Monica Airport Section 13
13-3 Airport Influence Zones, Santa Monica Airport Section 13 13-4 Airport Noise Contours, Santa Monica Airport Section 13 Note: Most of these maps were derived from publicly available sources. Care was taken in the creation of these maps, but the maps are provided "as is." Neither the City of Santa Monica nor Earth Consultants International can accept any responsibility for errors, omissions or positional accuracy, and therefore, there are no warranties that accompany these maps. Although information from land surveys may have been used in the creation of these maps, this does not mean that the maps represent or constitute a land survey. Users are cautioned to field verify the information on these products before making any decisions.

Vulnerability Assessment / Inventorying Assets
This is a combination of hazard identification with an inventory of the existing property development(s) and population(s) exposed to a hazard. The city of Santa Monica is built out, so new development, if and when it occurs, is in the form of infill or replacement of existing structures. Redevelopment provides an opportunity to build more seismically resistant structures, potentially with sustainable design components that make better use of existing resources, and that incorporate some of the new technologies aimed at reducing the impacts of ground shaking, wildfires, and climate change.

During the vulnerability assessment it is especially important to assess the expected performance of critical facilities. Critical facilities provide essential products and services to the general public that are necessary to preserve the welfare and quality of life, and fulfill important public safety,

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emergency response, and/or disaster recovery functions (additional information on critical facilities is provided in a subsection below). The critical facilities in and near Santa Monica have been identified and are illustrated on Figure 3-1 and Plate H-3 (Appendix H).

It is important to realize that in the urban setting that defines Santa Monica and the surrounding Los Angeles metropolitan area, a large-scale disaster, such as an earthquake, reservoir failure or pandemic, will not be confined to corporate boundaries. Differences in the magnitude of the disaster, however, will be defined, potentially in great part, by how each city in the impacted area has prepared for, responds to, and recovers from the event. Thus, having a detailed plan (or plans) in place that addresses the specific vulnerabilities of the City, and provides mitigation measures that are implemented to reduce the hazard to critical facilities and other public and private properties, can make the community significantly more disaster-resistant. That is the main goal of this Plan.

Risk Analysis
The purpose of this task is to estimate the potential losses in a geographic area over a given period of time by assessing the damage, injuries, and financial costs likely to be sustained should a disaster occur. This level of analysis involves using mathematical models. The two measurable components of risk analysis are magnitude of the harm that may result and the likelihood of the harm occurring.

Describing vulnerability in terms of dollar losses provides the community and the State with a common framework by which to measure the potential effects of a given hazard on the assets in the area.

Loss estimates for the city of Santa Monica were conducted for the hazards of earthquakes (Section 6), tsunami (Section 7), and floods (Section 8). Four earthquake scenarios, two tsunami scenarios, and two flooding scenarios were considered. These estimates were done using HazUS, a standardized methodology for loss estimation based on a geographic information system (GIS).

HazUS was created as a project of the National Institute of Building Sciences, funded by the Federal Emergency Management Agency (FEMA), and it is based on guidelines and procedures developed to make standardized loss estimates at a regional scale (allowing estimates to be compared from region to region). HazUS is designed for use by State, regional and local governments in planning for loss mitigation, emergency preparedness, response and recovery. HazUS addresses nearly all aspects of the built environment, and many different types of losses. These HazUS components have been tested against the experience of several past disasters, and against the judgment of experts.

The other hazards addressed in this Plan were assessed either quantitatively where data were available, or lacking any data at all, qualitatively. For example, to estimate the costs associated with a windstorm event, the City researched and compiled costs incurred during previous recent past windstorm events, with an emphasis on the costs borne by the City to respond to and cleanup debris.

These figures were incorporated into the report. A similar approach was used for the sections on landslides and hazardous materials, and to some extent for the coastal flooding section, as the City has been impacted in the past by these events. As part of its Local Coastal Program Land Use Plan, the City had previously estimated the costs of sea-level rise; those figures informed the sea-level vulnerability assessment presented in this Plan. Estimates of the current cost of the properties likely to be impacted by some hazards were also conducted using Crisis Track®, a GIS-based disaster management software that uses tax data to estimate the cost of structural damage in a disaster.

Costs associated with some regional hazards such as extreme heat events and drought are far more difficult to estimate. In these cases, the Plan discusses the impact that these hazards may have on

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the community, and more significantly, on vulnerable populations, but does not provide dollar loss amounts.

Assessing Vulnerability / Analyzing Development Trends
This task provides a general description of land uses and development trends within the community so that mitigation options can be considered in land use planning and future land use decisions.

This Plan provides comprehensive description of the character of Santa Monica in the Community Profile section (see Section 2). This description includes the geography and environment, population and demographics, land use and development, housing and community development, employment and industry, and transportation and commuting patterns. Changes to the region that have occurred since the 2016 Plan was completed (and the 2010 Census considered in the 2016 Plan) are emphasized. Analyzing these components in Santa Monica can help identify areas where progress has been reported in the past decade, and potential problem areas that still need to be addressed and mitigated. The end result is that this analysis can guide the selection and prioritization of the action items considered for this five-year Plan, and their implementation and incorporation into other community development plans.

Hazard assessments are subject to the availability of hazard-specific data. Gathering data for a hazard assessment requires a commitment of resources on the part of the community being analyzed, in addition to participating organizations and agencies. Each hazard-specific section of the Plan includes a section on hazard identification using data and information obtained from City, County or State agency sources.

There are numerous strategies that Santa Monica can take to reduce risk. These strategies are described in the action items presented in Section 4, classified by hazard type and priority. Action items that address two or more hazards simultaneously are also presented in Section 4. Mitigation strategies can help reduce disruption to critical services, reduce the risk to human life, and alleviate damage to personal and public property and infrastructure.

CRITICAL FACILITIES AND INFRASTRUCTURE
Critical facilities are those parts of a community's infrastructure that must remain operational after a disaster. Critical facilities include hospitals, fire and police stations, emergency operation centers, communication centers, and schools, especially if used as shelters. A vulnerability assessment for these facilities involves comparing the locations of these facilities to the hazardous areas identified in the city. Critical facilities can be subdivided into several categories; those often considered in risk assessments include:
• High-risk facilities, if severely damaged, may result in a disaster far beyond the facilities themselves. Examples include power plants, dams and flood control structures, freeway interchanges, bridges, and industrial plants that use or store explosives, toxic materials or petroleum products. Although not located in the city of Santa Monica, catastrophic failure of Stone Canyon Dam would impact the eastern portion of the city, as discussed in Section

8. • Facilities critical to government response and recovery activities (i.e., life safety and property and environmental protection) include: 911 (or public safety communications) centers, emergency operations centers, police and fire stations, public works facilities, sewer and

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water facilities, hospitals, bridges and roads, and shelters. In the city of Santa Monica this category includes City Hall and City Hall East, Santa Monica Fire Department (SMFD) stations, the Santa Monica Public Safety Facility and Emergency Operations Center (EOC), Providence Saint John’s Health Center, and Santa Monica UCLA Medical Center. Public schools and libraries in the city also play an essential role in the event of an emergency or natural disaster event as they can serve as temporary shelters, mobile command centers, public information hubs, family reunification centers, etc. • Lifelines are those services that are critical to the health, safety and functioning of the community. They are particularly essential for emergency response and recovery after a disaster. Furthermore, certain critical facilities designed to remain functional during and immediately after a disaster, such as an earthquake, may be able to provide only limited services if the lifelines they depend on are disrupted. Lifeline systems include water, sewage, electrical power, communication, transportation (highways, bridges, railroads, and airports), natural gas, and liquid fuel systems. In Santa Monica, this would include the bridges and interchanges along Interstate 10 (I-10), the McClure Tunnel, Pacific Coast Highway, and the Moomat Ahiko Way. If any of these structures collapsed as a result of earthquake-induced strong ground shaking, or were obstructed by a large slope failure, traffic between the different areas of the city connected by these structures would be affected, if not completely cut-off, which would hinder access by emergency response vehicles. Casualties could also be expected if these structures collapsed. Other facilities in Santa Monica that also fall in this category include the Santa Monica Airport, the City Yards, the Arcadia Treatment Plant, the Big Blue Bus Yards, the City’s water reservoirs, the Santa Monica Urban Runoff Recycling Facility, and the Sustainable Water Infrastructure Project.

Most of the critical and essential facilities listed above that are in or near the city of Santa Monica are shown on Figure 3-1. Other facilities that ideally also remain functional during and following a disaster, such as an earthquake, because of their potential impact on the community are listed below.

These facilities are not included on Figure 3-1.
• High-occupancy facilities have the potential of resulting in a large number of casualties or crowd-control problems. This category includes high-rise buildings, large assembly facilities, and large multifamily residential complexes.
• Dependent-care facilities, such as preschools and schools, rehabilitation centers, prisons, group care homes, and nursing homes, house populations with special evacuation considerations.
• Economic facilities are those facilities that should remain operational to avoid severe economic impacts. These facilities include banks, archiving and vital record-keeping facilities, airports, and large industrial or commercial centers.

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Figure 3-1: Essential / Critical Facilities In and Near Santa Monica (also refer to Plate H-3 in Appendix H)

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FEDERAL REQUIREMENTS FOR RISK ASSESSMENT
Federal regulations for hazard mitigation plans outlined in 44 CFR Part 201 include a requirement for risk assessment. This requirement is intended to provide information that will help communities identify and prioritize mitigation activities that will reduce losses from the identified hazards. There are seven top-level natural hazards profiled in this Plan, including earthquakes (Section 6), tsunami (Section 7), floods (Section 8), landslides (Section 9), fires (Section 10), and severe weather and climate change (both addressed in Section 11). This Plan also addresses two human-caused possible hazards, namely hazardous materials releases (Section 12), and airport hazards (Section 13). Several of these hazards can occur simultaneously or consequentially, in what is referred to as a cascade (or cascading) event. Thus, for example, an earthquake could result in the accidental release of hazardous materials from damaged pipelines or overturned containers, and/or trigger several structure fires, and an intense precipitation event, such as that associated with an atmospheric river, could trigger the failure of a water retention structure that in turn would result in inundation of areas down-gradient.

The Federal criteria for risk assessment and information on how Santa Monica’s Natural Hazard Mitigation Plan meets those criteria are outlined in Table 3-4 below.

Table 3-4 - Federal Criteria for Risk Assessment
Section 322 Plan
Requirement How is this addressed?
Identifying Hazards
The hazard sections (Sections 6 through 13) provide a description of the natural or human-caused events that could affect the Santa Monica area, and their potential impact on the city of Santa Monica. To the extent GIS data are available for these hazards, maps that identify the areas most likely to be impacted by each hazard have been developed for the city of Santa Monica. These Hazard Maps are listed in Table 3-1 and are included in Appendix H. Note that some potential hazards, such as windstorms, are not geographic-specific and thus cannot be mapped.

Profiling Hazard Events
Each hazard section (Sections 6 through 13) includes documentation on the history of past hazard events, and the causes and characteristics of the hazard in the city of Santa Monica and/or in the Los Angeles region.

Assessing Vulnerability:

Identifying Assets
Where data are available, the vulnerability assessment for each hazard addressed in the mitigation plan includes an inventory of critical facilities within hazardous areas. Each hazard section provides information on vulnerable areas in the city and the impact that the hazard may have on vulnerable populations. Prioritized mitigation actions for these hazards are provided in Section 4.

Assessing Vulnerability:

Estimating Potential Losses
The Risk Assessment Section of this Plan (Section 3) identifies key critical facilities and lifelines in the city and includes a map of these facilities.

Vulnerability assessments have been completed for the hazards addressed in the plan. HazUS-based quantitative estimates were conducted for the earthquake (Section 6), tsunami (Section 7) and flood (Section 8) hazards.

Estimates of the potential losses and costs to respond and/or recover from the remaining hazards (Sections 9 through 13) are based on quantitative data collected by the City for past events, or qualitative data if figures were not available.

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Section 322 Plan
Requirement How is this addressed?
Assessing Vulnerability:

Analyzing Development
Trends
The Community Profile Section of this Plan (Section 2) provides a description of the city’s geography and environment, and historical trends in the City’s population and demographics, land use, housing and community development, employment and industry, and transportation and commuting patterns.

SUMMARY OF RISK ASSESSMENT FOR THE CITY OF SANTA MONICA Local Disaster (or Hazard) Mitigation Plans such as this one are to evaluate the hazards that are most likely to impact the community for which the Plan is being prepared. There are many types of natural hazards, but not all apply to a given area. Earthquakes typically pose the greatest challenge because they occur with little or no warning, and can set into motion linked, cascading events that disrupt other natural and man-made hazards that also have the potential to cause damage to a community.

Analysis conducted for this report shows that an earthquake on the section of the Santa Monica fault that extends through the city, combined with fault sections to the east and west, would cause significant damage to Santa Monica and the northern Los Angeles region. In most parts of the city, shaking will be severe, whereas in those areas within about ½ mile from the fault zone, ground shaking is expected to be violent. If the Santa Monica fault ruptures to the ground surface, the ground deformation will damage structures, streets, and utilities that straddle the fault traces.

An earthquake on the offshore section of the Palos Verdes fault in the Santa Monica Bay could also be a worst-case earthquake scenario for Santa Monica because, in addition to strong ground shaking, the earthquake could trigger a locally generated tsunami that could cause extensive loss of life along the beach. If this earthquake and tsunami event occur at a time when the beach is crowded with day visitors, the loss of life could be in the thousands. Both the Santa Monica and Palos Verdes fault earthquake scenarios discussed here, in addition to earthquakes on other nearby seismic sources, could trigger a sequence of events, including the unintentional release of hazardous materials, structure fires, and the catastrophic failure of water storage facilities.

Santa Monica is susceptible to several hazards other than seismic, although the consequences of these other hazards will be less regionally extensive. The risk that several of the hazards pose to critical facilities in and near Santa Monica are summarized in Table 3-5, below. Some of these hazards, like liquefaction, only occur in response to seismic shaking. Other hazards can be triggered by seismic shaking, but can also happen in response to some other causes, as described further below:
• Slope instability – which can occur in response to storms, human activities, or ground shaking
• Hazardous materials release – which can occur due to an accident on the I-10 or major roadways through the city, an intentional or unintentional release at one of the industrial or commercial facilities using or storing hazardous materials, or as a result of a flood event, inundation due to catastrophic failure of a water storage facility, seismic shaking, or earthquake-induced ground deformation (such as fault rupture, liquefaction, or landsliding), and

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• Flooding – due to coastal storms, El Niño-related storms, atmospheric rivers, or the catastrophic failure of a water storage facility or debris basin.

Wildfires historically have not occurred in Santa Monica proper but have occurred in the Santa Monica Mountains to the north, most recently within about 1/2 mile of the city. Some of the water storage facilities that supply water to Santa Monica are located in or near areas that could be impacted by wildfires. These facilities are identified in Table 3-5. Structure fires are not included in Table 3-5 because these can occur anywhere in the city and typically can be contained to the structure of origin with prompt response from the SMFD. However, it is important to remember that an earthquake can be followed by structure fires ignited by fallen and arcing electric lines, gas leaks, chemical reactions, and toppled water heaters and other appliances. If several structure fires following an earthquake occur simultaneously throughout the city, these could quickly overwhelm the local fire department, especially if emergency response personnel are at the time engaged in their post-earthquake immediate assessment of critical facility damage. The SMFD’s second priority following an earthquake is to respond to structural fires, and their third priority is to conduct search and rescue operations. Thus, search and rescue operations in the first few hours after a significant earthquake are usually conducted by neighbors and family members. Structure fires are particularly dangerous in heavily developed, older areas where buildings are most often not constructed of fireresistant materials and are located close together.

Table 3-5 lists the following natural and man-made hazards: Ground shaking, surface fault rupture, liquefaction, tsunami, coastal flooding, dam inundation, slope instability, wildfire susceptibility, sealevel rise, potential exposure to hazardous materials, and exposure to airport hazards.

Table 3-5 does not include severe weather (e.g., strong Santa Ana winds) or hazards related to climate change as these are either regional in nature (e.g., drought, extreme heat, etc.) or localized in their impact but difficult to predict where they will strike (e.g., tornadoes). Strong winds, unlike earthquakes and flooding, occur often. Although high winds are regional in extent, damage as a result of high winds tends to be localized. The costs associated with wind damage are, on a per event basis, fairly small, but given their frequency of occurrence, over the long-term, costs associated with wind damage can add up. Similarly, the severe weather hazards of extreme temperatures and drought are regional in extent, but the damages tend to be localized.

As mentioned before, the costs associated with extreme temperature and drought events are hard to quantify. Given the regional impact of these events, communities may feel powerless to mitigate them. However, there are a variety of strategies that communities can implement to reduce the impact that high or excessive heat and drought events may pose on their residents. Some of these potential mitigation actions are discussed in Section 11; specific actions that Santa Monica has chosen to implement in the next five-year cycle are listed in Section 4.

Natural hazard mitigation strategies can reduce the impacts concentrated at critical facilities and public infrastructure, in addition to large employment and industrial centers that provide the economic core of the region. Natural hazard mitigation for industries and employers may include developing relationships with emergency management services and their employees before disaster strikes, and establishing mitigation strategies together. Collaboration among the public and private sector to create mitigation plans and actions can reduce the impacts of natural hazards.

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Explanation for abbreviations used in Table 3-5:

Y = Yes; N = No
S = Severe; M = Moderate; m = Minor
The entire Santa Monica area can experience ground shaking as a result of an earthquake on any of several regional faults; however, sites within ½ mile of the Santa Monica fault will experience severe ground shaking. These sites are identified with an “S” for Severe.

For reference to the various hazards included in this Table, refer to the hazards sections in Volume II and the figures therein. The regional extent of several of the hazards as it pertains to the city of Santa Monica is also highlighted in some of the plates included in Appendix H. Refer to Table 3-1 for a list of these figures and plates.

A site marked “Y” for Hazardous Materials is located within about ¼ mile of a facility that is listed as a Toxic Release Inventory (TRI) site or a large generator of hazardous materials, or is located within ¼ mile of the crude oil pipeline that extends through the city (see Section 12). Sites that have reported a leak (typically of fuel) from an underground storage tank are not considered a potential source of contamination to nearby facilities because the leak is confined to the underlying soil (and maybe groundwater) and as a result, is not expected to pose an inhalation or skin-contact hazard.

Sites marked with a “Y” for Airport Hazards are located in or within about ¼ mile of the runway protection zone, airport influence zone, or inner safety zone.

Some of the critical facilities are not located directly in an area susceptible to a given hazard, but are located nearby, and access to/from the facility could be hindered. For example, surface fault rupture, landslides, and dam inundation all have the potential to impact traffic patterns and hinder access to the hospitals that serve Santa Monica.

All properties and facilities in Santa Monica are susceptible to the effects of severe weather, including strong winds, extreme heat, and drought. The damages resulting from severe weather are expected to be significantly less than those resulting from an earthquake, however.

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Table 3-5: Critical Facilities In and Near Santa Monica at Potential Risk from the Hazards Discussed in this Plan Map
Identifier Critical Facilities, Schools and Libraries
Ground Shaking
Surface Fault
Rupture
Liquefaction
Tsunami
Coastal Flooding
Dam Inundation
Slope Instability
Wildfire
Susceptibility
Flooding due to
Sea-Level Rise
Near Hazmat Site
or Oil Pipeline
Airport Hazard
Facilities Essential to Government and Healthcare Response PS/EOC1 Police Station/Public Safety Facility/ Emergency Operations Center, 333 Olympic Drive 0BY N N N N N Y, m N N Y N
EOC2/L2 Alternate Emergency Operations Center 2 at Main Library, 601 Santa Monica Boulevard 1BY N N N N N N N N Y N
EOC3 Alternate Emergency Operations Center at SM Airport, 3223 Donald Douglas Loop South 2BY N N N N N N N N Y Y
CH City Hall & City Hall East, 1685 Main Street 3BY N N N N N Y, m N N Y N FS-1 Fire Station #1, 1337 7th Street 4BY N N N N N N N N Y N FS-2 Fire Station #2, 222 Hollister Avenue Y N N N N N N N N Y N FS-3 Fire Station #3, 1302 19th Street Y N N N N N N N N Y N FS-5 Fire Station #5, 2450 Ashland Avenue Y N N N N N N N N Y Y FS-7 Fire Station #7, 1100 Palisades Beach Rd Y N Y Y Y N Y N Y N N FTA Fire Training Academy, 2500 Michigan Avenue Y N N N N N N N N Y N HP Police Harbor Patrol, 402 Santa Monica Pier Y N Y Y Y N N N Y N N CC Los Angeles County Court House, 1725 Main Street W Y N N N N N N N N Y N PSJHC Providence Saint John’s Health Center, 2121 Santa Monica Blvd. Y, S N N N N N N N N Y N UCLA UCLA Santa Monica Medical Center, 1250 16th Street Y, S N N N N N N N N Y N AS Santa Monica Animal Shelter, 1649 9th Street Y N N N N N Y N 6BFacilities Critical to Utility and Transportation Operations SMCY Santa Monica City Yard, 2500 Michigan Avenue Y N N N N N N N N Y N ACT Arcadia Treatment Plant, 1228 South Bundy Dr., Los Angeles Y, S Y Y, m N N N N N N Y N MOR Mt. Olivette Reservoir, 924 Franklin Street Y, S Y N N N N Y Y, m N N N RR Riviera Reservoir, 1252 Capri Drive, Pacific Palisades Y, S N Y N N Y Y Y N Y N SVR San Vicente Reservoir, San Vicente Blvd. and 26th Street Y, S N N N N N N Y, M N Y N BPS Booster Pump Station, San Vicente Blvd. and 25th Street Y, S N N N N N N Y, M N Y N CWF Charnock Well Field/Treatment Plant, 11375 Westminster Avenue, Los Angeles Y N N N N Y N N N N N PPT Penmar Park Tank, 1341 Lake St, Venice Y N N N N Y, m N Y, m N N Y SWIP Sustainable Water Infrastructure Project
1771 Main Street (includes Advanced Water Treatment Facility) Y N N N N N N N N Y N SMURRF Santa Monica Urban Runoff Recycling Facility, 1623 Appian Way Y N N N N N Y N N Y N

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Map
Identifier Critical Facilities, Schools and Libraries
Ground Shaking
Surface Fault
Rupture
Liquefaction
Tsunami
Coastal Flooding
Dam Inundation
Slope Instability
Wildfire
Susceptibility
Flooding due to
Sea-Level Rise
Near Hazmat Site
or Oil Pipeline
Airport Hazard
SCE1 Southern California Edison (SCE) Colorado Substation, 1721 22nd Street Y N N N N N N N N Y N SCE2 SCE Santa Monica Substation, 853 Colorado Avenue Y N N N N N N N N Y N SCE3 SCE Ocean Park Substation at 3110 2nd Street Y N N N N N N N N N N SCE4 SCE Facility at 1425 Marine Street Y N N N N N N N N N Y SMA Santa Monica Airport, 3223 Donald Douglas Loop S Y N N N N N Y, m N N Y Y Bus Yard Big Blue Bus Yards, 1620 6th Street & 612 Colorado Ave. Y N N N N N N N N Y N Metro LA Metro Division 14 Facility, 1955 Centinela Avenue, Los Angeles Y N Y N N Y N N N Y N 7BPublic Schools K-12, Community College Primary Campuses, and Libraries S1 Edison Language Academy, 2402 Virginia Avenue Y N N N N N N N N Y N S2 Franklin Elementary, 2400 Montana Avenue Y, S Y N N N N N N N N N S3 Grant Elementary, 2368 Pearl Street Y N N N N N N 5BN N N N S4 John Adams Middle, 2425 16th Street Y N N N N N N N N N N S5 Lincoln Middle, 1501 California Avenue Y, S N N N N N N N N Y N S6 McKinley Elementary, 2401 Santa Monica Blvd. Y, S N N N N N N N N Y N S7 Olympic High School, 1900 Pico Blvd. Y N N N N N N N N Y N S8 Roosevelt Elementary, 801 Montana Avenue Y, S N N N N N N N N Y N S9 Santa Monica Alternative School House (SMASH), 721 Ocean Park Blvd. Y N N N N N N N N Y N S10 Santa Monica High School, 601 Pico Blvd. Y N N N N N N N N Y N S11 Will Rogers Elementary, 2401 14th Street Y N N N N N N N N N N SMC1 Santa Monica College (SMC), Main Campus, 1900 Pico Blvd. Y N N N N N N N N Y N SMC2 SMC Bundy Campus, 3171 S. Bundy Drive, Los Angeles Y N N N N N N N N Y N SMC3 SMC Performing Arts Center, 1310 11th Street Y N N N N N N N N Y N L1 Fairview Branch Library, 2101 Ocean Park Blvd. Y N N N N N N N N Y N L2 Main Library, 601 Santa Monica Blvd. Y N N N N N N N N Y N L3 Montana Branch Library, 1704 Montana Ave Y, S N N N N N N N N Y N L4 Ocean Park Branch Library, 2601 Main Street Y N N N N N N N N Y N L5 Pico Branch Library, 2201 Pico Blvd. Y N N N N N N N N Y N

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SECTION 4: GOALS and

MITIGATION ACTIONS

INTRODUCTION
The ultimate goal of Local Hazard Mitigation Plans is hazard mitigation. For the purposes of this study, this means a risk-based approach to reduce or eliminate, if possible, the long-term risk to life, property and infrastructure from natural and human-made hazards. Thus, a successful hazard mitigation strategy provides a mechanism by which, during the process of preparing for, responding to, and recovering from natural hazards, the community reduces its vulnerability to future hazard events. Historically, communities impacted by a natural or human-caused hazard will repair the damage and reconstruct to similar pre-disaster conditions. Such efforts may expedite the return to normalcy, but in the process engender a cycle of damage, reconstruction, and repeated damage.

Hazard mitigation involves the implementation of actions that enable the community to not only respond effectively to a disaster, but to recover in such a way that the post-disaster repairs and reconstruction truly strengthen it. This Local Hazard Mitigation Plan Update outlines opportunities that the City of Santa Monica can use to increase the community’s resiliency to future hazard events.

This section also provides information on the process used to develop the specific goals and action items aimed at reducing the impact of several hazards on the city of Santa Monica. The action items were developed after an in-depth review of the City’s vulnerabilities and capabilities as described in Sections 2, and 6 through 13, round-table discussions with the Resiliency Planning Committee, and input from members of the community received in response to surveys prepared by the City in support of the Safety Element of the General Plan and this update to the Local Hazard Mitigation Plan. For additional information on the Public Participation process, refer to Appendix B. Many of the action items identified herein were prioritized because it was recognized that their implementation would benefit a broad section of the City’s residents, with an emphasis on priority populations.

HAZARD MITIGATION OVERVIEW
Many Federal, State and local programs have been implemented over the years to reduce losses created by natural and human-made hazards in the city of Santa Monica. Several of these programs are described in detail in the appropriate sections of the Plan–the reader is referred to Sections 6 through 13 for additional information. The following sub-sections refer to some of the most significant programs and regulations that have been developed to encourage or require communities to manage and reduce some of the most common and costliest natural hazards. Each sub-section also describes how these programs are being implemented in Santa Monica.

National Flood Insurance Program
The National Flood Insurance Program (NFIP) was created by the U.S. Congress in 1968. Although a community’s participation in the NFIP is voluntary, in order to receive assistance and funding from FEMA following a flood, the community must participate in the program. The City of Santa Monica has participated in the NFIP since 1983 (City ID No. 060159). Development in the flood prone areas of the city is regulated in accordance with Chapter 7.68 – Floodplain Management Regulations of the City’s Municipal Code.

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The Community Rating System (CRS), implemented in 1990, is a voluntary part of the National Flood Insurance Program (NFIP) that seeks to coordinate all flood-related activities, reduce flood losses, facilitate accurate insurance rating, and promote public awareness of flood insurance by creating incentives for a community to pursue beyond the minimum requirements of the NFIP. CRS ratings are assigned on a nine-point scale, from 1 to 9, with 1 being the best rating. Residents who live within FEMA’s Special Flood Hazard Areas (SFHAs) receive a 5% reduction in flood insurance rates for every one-point improvement in the community’s CRS class. As a community engages in additional mitigation activities, its residents become eligible for increased NFIP policy premium discounts. The 2025 CRS Eligible Communities list includes Los Angeles County with a rating of 6 and City of Los Angeles with a rating of 7.

Beginning on April 1, 2022, FEMA began calculating NFIP flood insurance premiums using what they refer to as Risk Rating 2.0. This rating methodology calculates premiums for individual properties based on the property’s specific flood risk rather than being assigned a general risk category. Premiums are now calculated based on specific features of an individual property, including distance from water, type of flooding, flood frequency, structure foundation type, height of the lowest floor relative to BFE, prior claims, and the structure's replacement cost value. An analysis of the impacts of the new premiums on properties in Santa Monica shows that approximately 286 properties saw no increase or a very small increase in their 2025 flood insurance premiums compared to 2024, 37 properties saw a decrease in their monthly premiums of between $10 and about $100, and about 12 properties saw an increase of between $10 and $60 in their monthly premiums.

A property is considered a repetitive loss (RL) property if it has incurred two or more flood-related claims exceeding $1,000 each, paid by the National Flood Insurance Program (NFIP) within any ten-year rolling period since 1978. As of December 9, 2024, FEMA’s records of repetitive loss properties0F
1 in the city of Santa Monica suggest one single-family residence built in 1937 that is located in census block 060377014023 and SFHA VE has filed two claims of more than $1,000 each within a ten-year period, with the most recent claim dating from March 2, 1983. Based on these data, there are no properties in Santa Monica that have had a flood-related claim with FEMA in more than 40 years.

Senate Bill 1241 and Assembly Bill 38
At the State level, and to address the increasing losses associated with wildfires at the wildlandurban interface, Senate Bill 1241 (2012 Kehoe Statutes) requires that cities revising their Housing Element of the General Plan on or after January 1, 2014 also review and update their Safety Element to address the risk of fire in State Responsibility Areas and in very high (VH) fire hazard severity zones (FHSZs).

Santa Monica’s 2021-2029 Housing Element was adopted by City Council on October 2022, with the adoption prompting the update of the City’s Safety Element. The revised Safety Element was completed in August 2024, and adopted in February 2025. In January 2025, the region was impacted by the devastating Palisades fire, which burned to within about 350 feet of the city’s northern boundary. Prior to this fire, the entire city of Santa Monica was not considered susceptible to wildfire hazards. In March 2025, CAL FIRE issued its Phase 4 maps reclassifying southern California’s fire 1 Based on a review of the csv file from https://www.fema.gov/openfema-data-page/nfip-multiple-loss-propertiesv1, accessed May 5, 2025.

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hazard severity. The new map for the Malibu-Santa Monica region places the northernmost portion of Santa Monica, generally north of Georgina Avenue, within a VHFHSZ, and another approximately 600-foot-wide swath parallel to the southern boundary of the VHFHSZ within a high FHSZ. The next about 600 feet south of that zone is now mapped as within a moderate FHSZ. These changes are discussed in Section 10, and the new mapping is shown both as Plate H-17 in Appendix H, and as Figure 10-4 in Section 10.

As a result of this new map, the provisions of Senate Bill (SB) 1241 (2012) and Assembly Bill (AB) 38 (2019) now apply to the northernmost portion of the city of Santa Monica. This means that the City now needs to address wildfire hazards and risks, adopt policies designed to address and reduce the risks associated with wildfires, and require disclosures during real-estate transactions. This is addressed in this Plan update (see Section 10 and the Action Items in this Section 4 that address fires in the very high FHSZ. The 2025 Safety Element update, in accordance with California Government Code (GC) § 65302.15, also identifies evacuation routes from the northern reaches of the city that local residents are encouraged to use in the event of a wildfire in that area.

Assembly Bill 2140
AB 2140 (2006) provides a financial incentive for local agencies to adopt a Local Hazard Mitigation Plan as a component of the Safety Element of their General Plan. The City of Santa Monica adopted its latest Safety Element of the General Plan in February 2025. The City will link this Local Hazard Mitigation Plan by reference to their 2025 Safety Element, especially since several of the policies in the Safety Element are included as action items in this document.

California Public Resources Code Chapter 7.5, Sections 7.5 and 7.8 These sections are also known as the Alquist-Priolo Earthquake Fault Zoning Act (Section 7.5) and Seismic Hazards Mapping Act (Section 7.8). The Alquist-Priolo Earthquake Fault Zoning Act (APEFZA) prohibits the placement of developments and structures for human occupancy (with certain exceptions) across the trace of Holocene-active1F 2 faults. The Seismic Hazards Mapping Act
(SHMA) requires the identification and mapping of areas subject to the effects of strong ground shaking, liquefaction, landslides or other earthquake-related ground failure so that cities and counties can encourage land use management policies and regulations aimed to reduce or mitigate these hazards. The SHMA also indicates that the State Geologist may include information on the potential effects of tsunami and seiche for use by local governments if the data are available from other sources. Both acts require that the transferor or the agent for a transferor of real estate property located in either one or both zones disclose this fact to prospective buyers.

The City of Santa Monica requires fault investigations for all developments or re-developments of habitable structures, even of single-family residences if more than two-stories high, located within the State-mapped APEFZ. The City also requires that geotechnical studies of properties located within a State-mapped seismic hazard zone include an analysis for liquefaction or slope stability, as appropriate, with the report providing engineering solutions to mitigate these hazards. These hazards and requirements are discussed in more detail in Sections 6 (fault rupture, liquefaction) and 9 (landslides). Tsunamis are covered in Section 7.
2 Holocene-active faults are faults that have moved at least once in the past 11,700 years.

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PLAN COMPONENTS
Mission
The mission of the city of Santa Monica’s Local Hazard Mitigation Plan is “to promote sound public policy designed to protect citizens, critical facilities, infrastructure, private property, and the environment from natural and human-made hazards.”
This is being achieved by increasing public awareness, documenting the resources available for risk reduction and loss prevention, and identifying and implementing activities that will help the city of Santa Monica become a safer, more disaster-resilient and sustainable community.

Goals
The goals are stepping-stones between the broad direction of the mission statement and the action items. The Plan Goals help guide the direction of future activities aimed at reducing risk and preventing loss from natural hazards. Essentially, the goals provide a framework by which to promote sound public policy designed to protect the city’s residents and visitors, the city’s critical facilities and infrastructure, private property and the environment from the natural and human-made hazards recognized as most likely to impact the area. The goals listed here serve as checklist items that City staff, Council members and the public can refer back as City departments and other organizations begin implementing the action items. These goals have been prioritized by City staff, with the most important goal (protect life and property) listed first. Other goals include strengthen emergency services, increase public awareness, seek public participation, partnerships and implementation, and natural systems. Elements of each of these goals are described further below.

Protect Life and Property
• Implement activities that assist in protecting lives by making homes, businesses, infrastructure, critical facilities, and other property more resistant to natural and humancaused hazards. • Reduce losses and repetitive damages from chronic (frequently recurring) hazard events while promoting insurance coverage for catastrophic hazards.

Strengthen Emergency Services
• Establish policy to ensure that mitigation projects to strengthen critical and essential facilities, services, and infrastructure, where needed, are considered and prioritized. • Coordinate and integrate hazard mitigation activities, where appropriate, with emergency operations, plans and procedures.
• Strengthen emergency operations by increasing collaboration and coordination among public agencies, non-profit organizations, businesses, industry, and residents.

Increase Public Awareness
• Develop and implement educational and outreach programs that increase public awareness of the risks associated with natural and human-made hazards.

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• Keep the public informed of hazard mitigation initiatives and activities through community meetings, local newspapers, the City’s website, newsletters, utility bill inserts, and other similar media.
• Provide information on tools, partnership opportunities, and funding resources that can help in the implementation of mitigation activities.

Seek Public Participation
• Obtain input from City staff and the public when updating the Local Hazard Mitigation Plan and other similar efforts, including during the process of developing and prioritizing the Plan goals and action items and the assignment of responsibilities, taking into consideration the expected efficacy of the proposed action items and the proposed timelines.

Foster Partnerships and Implementation
• Continue to foster communication and coordination among and within City departments, other agencies, residents, non-profit organizations, businesses, and industry so that there is a mutual, vested interest in participating in the implementation of the action items. • Encourage leadership within public and private sector organizations to prioritize and implement local, county, and regional hazard mitigation activities.

Preserve and Enhance Natural Systems
• Continue to balance the need to protect and manage the natural resources and areas in the city (such as the beach, sand dunes and the bluffs) with the need for hazard mitigation to protect lives and property, by reducing conflict that may arise between these two objectives. • Whenever possible, preserve, rehabilitate, and enhance the natural systems in ways that also provide natural hazard mitigation functions.

Components of the Plan’s Actions
The Actions are activities that City departments, in some cases in coordination with other organizations, businesses and residents, can implement to reduce risk. Each action item includes an estimate of the length of time it will take to implement. All action items identified by Santa Monica’s multi-sector Resilience Planning Committee (RPC) are short-term, meaning that City staff hope to implement them within the next two to five years. Although optimistic, this aggressive schedule illustrates the City’s strong desire to reduce several of its identified hazard vulnerabilities as soon as possible.

As discussed above, there are several mitigation activities mandated or recommended by Federal, State or local statutes that the City conducts on an on-going basis as part of its permitting and development processing. Those activities will continue to be implemented as they are an important component in the City’s efforts to reduce its vulnerability to natural and human-made disasters. The action items identified for this 2025-2030 Plan that were identified by the RPC as being high priority, are discussed further below.

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The action items are listed together to make this document as user-friendly as possible, with the goal of providing the reader and City staff in particular, with a concise document that clearly establishes the path the City has chosen to reduce its vulnerability to specific natural and human-made hazards over the next five-year period. It also allows the City departments and organizations identified as responsible for the implementation of the action items to see and manage their charges more effectively.

Note that several of the action items identified address several hazards at once, and thus fall under the Multi-Hazard (MH) umbrella. Because cities typically have limited funding and staffing resources that constrain the effective implementation and management of mitigation actions, MH action items are typically more attractive than those that only address one hazard, with MH action items more likely to be implemented first. Limited financial resources often also force jurisdictions and agencies to review and select the most cost-effective mitigation projects first, in essence prioritizing mitigation projects by their return on investment. The challenge is to maintain a balance between mitigating projects that can be implemented readily and for a relatively small amount of money, with longerterm projects that cost more but have the potential to more significantly reduce the City’s vulnerability to natural hazards. These realities should be kept in mind as the City works through its planned implementation of the action items identified.

LHMP activities may be considered for funding through Federal, State and private grant programs, and when other funds are made available through the City. To help ensure activity implementation, each action item includes information on the City department(s) or division(s) responsible for developing, implementing, and managing that activity. Upon implementation, the implementing department or division may look to partner with other organizations for resources and technical assistance. A description of possible partner organizations is provided in Appendix A, the Resource Directory of this Plan.

Many of the action items included here mirror or complement the policies in the City’s 2025 Safety Element of the General Plan and the City’s Municipal Code, but wherever possible, have been written to be more specific in that they identify the coordinating organization, timeline for implementation, goal(s) being addressed, and potential constraints, in accordance with FEMA’s requirements. 2025 Safety Element policies mirrored in the LHMP action items are also identified.

In the Safety Element, the policies are not prioritized, and are typically not assigned to a specific department. Other action items herein were developed by the RPC in response to the data collection and research process whereby specific concerns were identified, as a result of input from City departments during meetings of the RPC, or in response to input from the public during the public participation process. Mitigation actions specific to wildland fire were developed in response to the 2025 Palisades fire and input received at that time from residents and other stakeholders in the city.

Coordinating Organization
The coordinating organization is the City department, division, or other agency that is willing and able to organize resources, find appropriate funding, or oversee activity implementation, monitoring, and evaluation. Coordinating organizations may include City departments, and/or other local or regional agencies, and private entities that are capable of, or responsible for, implementing activities and programs.

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Timeline
Action items typically include both short- and long-term activities. The City of Santa Monica will strive to complete the mitigation actions that are identified in this Section in five years, by 2030.

Each action item listed on Table 4-5 includes an estimate of the timeline for implementation as provided by members of the Plan’s RPC. During the yearly review of the Plan, the City will assess whether implementation of some of the action items needs to be continued into the next five-year plan based on progress made to that point, and in response to unanticipated funding or staffing constraints.

Plan Goals Addressed
The Plan goals addressed by each action item are included as a way to monitor and evaluate how well the Local Hazard Mitigation Plan is achieving its goals once implementation begins.

Constraints
Constraints to the immediate implementation of the action items are typical, usually because of limited resources, as described further below. Constraints may include a lack of City staff to do the work, lack of funds, vested property rights that might expose the City to legal action as a result of adverse impacts on private property, or as a result of other similar economic, political, social or legal reasons.

It is important to note that the City of Santa Monica’s General Fund has funding limitations based on existing constraints, existing City liabilities, and reductions in travel tax revenue. Currently, there is greater uncertainty on Federal grant funding and the organization of agencies that administer funding. Funding sources may be reduced, withheld, or eliminated. Projects are also dependent on City staff’s availability to work on these projects, which can be strained during periods of staffing turnover or when emergencies or unexpected events occur and staff time and resources are refocused on preparation, response and recovery activities (as an example, the COVID-19 pandemic or recent Palisades fire). City staff who primarily oversee hazard mitigation projects are also expected to take on a large amount of work to safely execute major special events in the next five (5) years, including the 2026 FIFA World Cup and the 2028 Olympics.

PRIORITIZATION PROCESS
After the consultant gave a presentation to the Resilience Planning Committee (RPC) describing the hazards, risks, and vulnerabilities that were identified as part of the LHMP preparation process2F 3 , the
committee members were asked to divide into several smaller groups. The groups were loosely formed based on area of expertise (i.e., firefighters together, engineers from building safety and public works together, environmental planners together, etc.). Each group was asked to identify potential mitigation actions that address the hazards that they most closely aligned with based on their background and role at the City, with the action items designed to specifically address the vulnerabilities identified during the risk assessment.
3 The PowerPoint presentations and additional information regarding these workshops, meetings, and participants are all contained in Appendix B.

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The members of the RPC were asked to keep in mind the following requirements as they prepared their proposed action items:
• The Plan must include a wide, comprehensive range of action items or projects, and the action items must cover a wide range of the Plan goals, as discussed above • Every action item needs to identify who the responsible agency will be (no orphan actions allowed)
• Where possible, potential funding sources need to be identified • Potential constraints to the funding and overall implementation of the action item need to identified and discussed
• Every action item should have generalized timeline of its implementation, either as ongoing, short- and long-term, or as the calendar year when ideally the action item has been deployed and/or completed
• Potential action items should include activities designed to alleviate the long-term risk from climate change, and should also be sensitive to or benefit underserved communities in the city
• To identify appropriate action items and establish their priority, the RPC members were asked to refer to the STAPLEE (Social, Technical, Administrative, Political, Legal, Economic, and Environmental) process (see Tables 4-1 and 4-2). Although the specific grading scheme recommended by the STAPLEE process was not used, RPC members were encouraged to consider the criteria listed in Table 4-2 as they qualitatively weighted the action items proposed.

Table 4-1: Elements of the STAPLEE Process
SOCIAL Community Acceptance Effect on Segment of Population TECHNICAL Technical Feasibility Long-term Solution Secondary Impacts ADMINISTRATIVE Staffing Funding Allocated Maintenance/Operations POLITICAL Political Support Local Champion Public Support LEGAL State Authority Existing Local Authority Potential Legal Challenge ECONOMIC Benefit of
Action Cost of Action Contributes to Economic Goals Outside Funding Required ENVIRONMENTAL Effects on
Land/Water
Effect on
Endangered
Species
Effect on

HAZMAT /
Waste Sites
Consistent with
Community
Environmental Goals
Consistent with
Federal Laws
Table 4-2: Criteria to Consider as part of the STAPLEE Process CRITERIA SPECIFIC IMPACT Specific QUESTIONS to Consider for EACH IMPACT
Social
Acceptance Is the action perceived as socially acceptable to a wide segment of the population?
Effect on Segment of
Population
Is the action item likely to impact (positively or negatively) a particular segment of the population?
Technical
Feasibility Is the action feasible given our current knowledge or science? Long-Term Solution Is implementation of this action going to reduce the hazard permanently?

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CRITERIA SPECIFIC IMPACT Specific QUESTIONS to Consider for EACH IMPACT
Administrative
Staffing
Is there staff currently at the City doing this work? Does it involve 1 person, or more?
Is there staff currently at the City doing this work? Does the City need to hire someone to get the work done?
Funding allocated Is there funding currently allocated? Is the funding available sufficient to do the work without cutting corners?
Maintenance Does this action require constant maintenance and upgrade? Political
Public support Is the action going to be popular with the public? Political support Is the action going to be popular with the Mayor and City Council?
Legal
State authority Is there a State mandate or a recommendation to have this done?
Local authority Is there a local mandate or recommendation to implement this action
Possible legal action? Is this action likely to get challenged in court? Economic
Benefit What are the economic benefits of implementing this action?
Cost What are the economic costs of implementing this action? Outside Funding Is there outside funding available to implement this action? Environmental
Impacts on Environment
(Land, Water,
Endangered Species, etc.)
Does this action have a positive or negative impact on the environment?
Consistent with
Community's
Environmental Goals
Is the proposed action consistent with the City's
environmental goals?
RPC members were also asked to consider and include if at all feasible, several requests made by members of the community who had participated in the public workshops and surveys. Items on this list included:
• Information and training on:
 Insurance coverage and availability
 Preparing neighborhoods to help themselves
 Disaster preparedness for earthquake, fire, airplane crash, cyberattack, terrorist attack, armed shooter, emergency kits
• Distribution of supplies (hazard kits, water, battery backups) • Increased and recurrent communication on disaster preparedness • Increased enforcement and assistance with seismic retrofits • Upgrade / retrofit utilities, infrastructure
• Enact legislation making air conditioning mandatory in multi-residential buildings • Invest on measures to help City be more extreme-heat resistant • Improve street safety (more street lights, clear sidewalks, discourage loitering, manage crime) • Food resiliency programs, such as community gardens

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The potential action items identified by these breakout groups were compiled, and organized into major categories based on project type, as follows:
• Local Planning
• Local Assessment and Regulations
• Structure and Infrastructure
• Natural Systems Improvements
• Education and Awareness Programs, and
• City Readiness Initiatives
The potential action items identified by the RPC are summarized in Table 4-3 below.

Table 4-3: Complete List of Action Items Developed by the Resiliency Planning Committee Category Summarized Potential Action Item Abbreviation
Local Planning
Water deconfliction planning: Identify strategies for immediate and long-term local potable water services during disaster events; identify strategies to prioritize water usage during emergencies.

LP-1
Cooling/heating center plan: Develop plan and operational requirements to activate cooling/heating centers during extreme weather events.

LP-2
Evacuation plan and route plans: Evaluate multi-modal citywide evacuation procedures and create a citywide evacuation plan to implement evacuation procedures during emergency events.

LP-3
Santa Monica Airport (SMO) space design: In the planning of the SMO space, ensure that emergency preparedness, mitigation and response features are included.

LP-4
Stone Canyon Dam (SCD) plan and outreach: Create Citywide response plan for inundation due to failure of SCD, including educating residents within inundation zone.

LP-5
Local
Assessment and
Regulations
Resilient City facility design standards: Implement and enhance design standards for City-owned and/or City/tenant-operated facilities to make them more disaster-resilient. Prioritize seismic retrofits.

LAR-1
Targeted building code standards: Implement City building code requirements for critical and essential facilities to improve postdisaster operations.

LAR-2
Wildfire assessment: Conduct further assessment on Santa Monica wildfire hazards and risk to determine if future building code or other regulations should be recommended.

LAR-3
Building heating/cooling requirements: Explore health and safety standards for indoor and outdoor workers and residential properties to reduce injury/illness to residents during wildfire and extreme weather events.

LAR-4
Evacuation route street standards: Examine/implement street standards for properties along evacuation routes and other evacuation requirements such as street parking restrictions, valet requirements, emergency vehicle access, etc.

LAR-5
Santa Monica bluff and I-10 freeway slope mitigation: Continue to inspect and monitor bluff and I-10 freeway slope stability. Where necessary, implement actions to mitigate land instability, especially during rain and seismic events.

LAR-6

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Category Summarized Potential Action Item Abbreviation
Structure and
Infrastructure
Back-up utilities: Identify and create program to implement critical utility back-up systems at City facilities and essential/emergency community facilities, including microgrids, solar + storage, and other back-up sustainable utility resources.

SI-1
Tsunami alarm system: Implement siren warning system to alert public to evacuate Santa Monica beaches, Pier and low-lying areas in the event of tsunami warning or imminent threat, such as coastal inundation or landslide.

SI-2
Water infrastructure seismic assessment: Examine water system resistance to local seismic hazards, especially water infrastructure that crosses potential liquefaction zones and mapped traces of projections of the Santa Monica fault. Consider retrofitting older water pipelines and other strategies to address seismic vulnerabilities.

SI-3
Traffic/street light improvements: Harden street and traffic light infrastructure to prevent copper theft and resulting power disruptions.

SI-4
Natural Systems
Improvements
Natural dune restoration: Continue to expand Natural Dune Beach restoration project to protect beaches and beach-front properties from erosion, sea level rives, and coastal flooding.

NSP-1
Food resilience through community gardening: Increase production of food grown and donated from City-owned community gardens to local organizations to increase food resilience of vulnerable Santa Monica residents.

NSP-2
Education and
Awareness
Programs
Inclusive emergency communications: Conduct emergency response, mitigation, and preparedness outreach in multiple languages to better reach diverse Santa Monica communities, including international tourists.

EAP-1
School hazard mitigation education: Explore continuing or expanding SMMUSD’s Project Based learning program on natural hazards at public school venues.

EAP-2
Business and partner liaison program: Develop program/training for City emergency partners to serve as Emergency Operations Center liaisons or activate/organize a business operations center to address and communicate post-disaster needs.

EAP-3
City Readiness
Initiatives
Mitigation funding: Explore and identify sustainable ways to fund long-term City mitigation projects, including preventative maintenance programs.

CRI-1
Grant process improvement: Expand Citywide staffing resources and capacity to identify potential grant funding and
write/implement/monitor grant-funded projects.

CRI-2
Expand critical emergency management technologies: Expand City GIS mapping, staffing, training, and tools to better facilitate emergency planning and response activities, including use of public education/communications.

CRI-3
City department education: Implement regular education for City personnel on California Disaster Service Worker requirements and City department response plans.

CRI-4
Cyberterrorism assessment: Conduct assessment to determine vulnerabilities and risk cyberterrorism impacting City critical infrastructure.

CRI-5

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Following the workshop, the link to an online questionnaire including all identified potential actions was sent to all the members of the RPC. Each member was asked to rank the action items under each category based on perceived priority, with a value of one (1.0) indicating highest priority. The results of this effort were compiled, and the average priority value (and standard deviation from the average) for each action item was calculated. The results of this analysis are summarized in Table 4-4. The values used to classify the action items under each of the six categories as either high, medium or low priority are provided in Table 4-4, with the action items under each project type category with the lowest average values (closest to 1.0) were identified as top priorities. For the most part, all action items were identified as either high or medium priority. The relatively large standard deviations indicate that there were considerable differences in opinion among the RPC members as to which action items should be top priority, which is to say that all action items considered are deemed to have a high priority by a subset of the committee.

Table 4-4: Action Item Prioritization Results
Mitigation Action
Average
(Standard
Deviation)
Priority Ranking
Local Planning (High: 1.0-2.33; Medium: 2.34-3.63; Low: 3.64-5.0) Water deconfliction (LP-1) 1.61 (0.96) High
Cooling/heating centers (LP-2) 3.07 (1.27) Medium
Evacuation plans (LP-3) 2.11 (1.13) High
SMO space design (LP-4) 3.25 (1.29) Medium
SCD plan and outreach (LP-5) 3.28 (1.27) Medium
Local Assessment and Regulations (High: 1.0-2.66; Medium: 2.67-4.33; Low: 4.34-6.0) Resilient City facility (LAR-1) 2.11 (1.03) High
Targeted building code standards (LAR-2) 2.89 (1.42) High Wildfire assessment (LAR-3) 3.68 (1.70) Medium
Building heating/cooling requirements (LAR-4) 3.68 (1.67) Medium Evacuation route street standards (LAR-5) 3.04 (1.71) Medium Santa Monica bluff and I-10 slope mitigation (LAR-6) 2.11 (1.29) High Structure and Infrastructure (High: 1.0-2.0; Medium: 2.0-3.0; Low: 3.0-4.0) Back-up utilities (SI-1) 1.68 (0.82) High
Tsunami alarm system (SI-2) 2.71 (1.12) Medium
Water infrastructure assessment (SI-3) 1.39 (0.5) High
Traffic/street light improvements (SI-4) 2.68 (0.90) Medium Natural Systems Improvements (High: 1.0-1.3; Medium: 1.31-1.66; Low: 1.67-2.0) Natural dune restoration (NSP-1) 1.39 (0.5) Medium
Food resilience through community gardening (NSP-2) 1.71 (0.46) Low Education and Awareness Programs (High: 1.0-1.66; Medium: 1.67-2.33; Low: 2.34-3.0) Inclusive emergency communications (EAP-1) 1.46 (0.58) High School hazard mitigation education (EAP-2) 2.14 (0.76) Medium Business and partner liaison program (EAP-3) 1.93 (0.77) Medium City Readiness Initiatives (High: 1.0-2.33; Medium: 2.34-3.63; Low: 3.64-5.0) Mitigation funding (CRI-1) 1.92 (0.90) High
Grant process improvement (CRI-2) 3.14 (1.35) Medium
Expand emergency management technologies (CRI-3) 1.82 (1.02) High City department education (CRI-4) 3.0 (1.47) Medium
Cyberterrorism assessment (CRI-5) 2.54 (1.40) Medium

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Given these findings, generally those action items identified as top priorities under each category were selected as action items to be implemented in the next five (5)-year cycle, by 2030, and are included in the final list of action items in Table 4-5. In response to the Palisades fire and the new requirements from the State, some new action items not originally considered by the RPC that are specific to the management of wildfire hazards were added to the list also. 2025-2030 HAZARD MITIGATION ACTIONS
Table 4-5 lists the hazard mitigation actions that the City of Santa Monica has chosen to implement in the next five (5) years, through 2030. For each action item the City has identified the City division(s) responsible for implementation, and the main point of contact at that division. Potential funding sources are also identified, followed by the desired timeline for implementation. The last two columns in Table 4-5 identify which goals are being addressed by each specific action item, and the Safety Element policies that are being addressed, respectively. The following abbreviations, arranged in alphabetical order, are used to identify the City departments identified as responsible for implementation.

CDD Community Development Department
CMO City Manager’s Office
DOT Department of Transportation
ISD Information Services Department
OEM Office of Emergency Management
OSE Office of Sustainability & the Environment
PW Public Works
SMPD Santa Monica Police Department
SMFD Santa Monica Fire Department

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Table 4-5: Hazard Mitigation Actions, City of Santa Monica Action Item Responsible Division and
Division Point of Contact
Potential Funding Source(s) and
Constraints Timeline Plan Goals Addressed
Complementary
Safety Element
Policies
Local Planning
Water Deconfliction Planning
Identify strategies for immediate and long-term local potable water services during disaster events, such as seismic events, wildfire or drought. Identify water deconfliction strategy to prioritize water usage during emergencies (i.e. recreational pools vs firefighting needs).

PW/ Water Resources
Sunny Wang
Water fund 2026
Protect life and property
Emergency services
Public awareness
Policy 1.1
Policy 1.3
Policy 1.9
Evacuation Planning
Assess Santa Monica’s transportation network and multi-modal citywide evacuation routes identified by the City’s revised Safety Element. Create a citywide evacuation plan to meet anticipated demand during emergency events, such as a tsunami, dam inundation or wildfire.

Plan to include evacuation considerations for persons with access and functional needs, including those without access to private transportation, and persons living in assisted living and high-rise buildings. Publicize to the community.

CMO / Office of Emergency
Management (OEM), DOT,
SMPD
Lindsay Call
General fund
Constrained by available staff capacity across
departments for planning and implementation
2026
Protect life and property
Emergency services
Public awareness
Partnerships and
implementation
Policy 6.1
Policy 6.3
Santa Monica Airport Space Design
In the planning of the Santa Monica Airport space, ensure that emergency preparedness, mitigation, and response features are included, such as the storage of disaster cache supplies and space for emergency operations (owned/operated and available for use by public safety departments).

PW / Architectural Services
Amber Richane
General fund; park impact fees;
future grant opportunities
Constraints include limited available space;
balancing community needs
2029
Emergency services
Public awareness
Partnerships and
implementation
Policy 6.2
(Action 6.2.9)
Local Assessment and Regulation Projects
Santa Monica Bluffs and I-10 Freeway Slope and Brush Fire Mitigation Continue to inspect and monitor Santa Monica bluffs and I-10 Freeway slope stability and brush overgrowth. Where necessary, implement actions needed to mitigate land instability, especially during rain and seismic events, and clear brush and other debris to mitigate brush fires.

PW/ Engineering,
SMFD / Fire Prevention
Alex Nazarchuk,
Joe Cavin
General fund; Local return
Constrained by available funding; available
staff capacity for implementation
2030
Protect life and property
Emergency services
Partnerships and
implementation
Natural systems
Policy 1.6
Red Flag Warning Restrictions
Implement policy that during any Red Flag Warning, restrictive measures will be implemented to reduce fire ignition opportunities and facilitate rapid first responder response activities.

Restrictions to be considered include, but are not limited to, parking restrictions in very high hazard zones and evacuation routes, leaf blower bans, and construction activity bans.

SMFD / Fire Prevention,

CMO / OEM
Joe Cavin,
Lindsay Call
Existing funds
Constrained by available staff capacity for
policy development; available staff capacity for
enforcement
2026
Protect life and property
Emergency services
Public awareness
Public participation
Partnerships and
Implementation
Policy 2.1
Policy 2.2
Policy 6.3
Resilient City Facility Design Standards
Implement and enhance a set of design standards for City-owned and/or City/tenant-operated facilities to make facilities more disaster-resilient, both to ensure their operability post-disaster and protect occupants. Prioritize seismic retrofits of public infrastructure and facilities to minimize potential damage, ensure protection of vulnerable populations, and continuity of government operations.

PW /Architectural Services
Amelia Feichtner
General Fund; future grant opportunities
Constrained by available funding; available
staff capacity for implementation
2028
Protect life and property
Emergency services
Public awareness
Partnerships and
Implementation
Policy 1.1
Policy 1.2
Policy 1.3
Policy 1.9
Policy 6.1
Policy 6.2
Structure and Infrastructure Projects
Water Infrastructure Seismic Assessment
Examine water system resistance to local seismic hazards, especially water infrastructure that crosses potential liquefaction zones and areas where traces or projections of the Santa Monica fault have been mapped. Consider retrofitting older water pipelines and other strategies to address identified seismic vulnerabilities.

PW / Water Resources
Sunny Wang
Water fund, future grant opportunities
Constrained by available funding 2029
Protect life and property
Emergency services
Public awareness
Policy 1.1
Policy 1.9

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Action Item Responsible Division and
Division Point of Contact
Potential Funding Source(s) and
Constraints Timeline Plan Goals Addressed
Complementary
Safety Element
Policies
Back up Utilities
Identify and create program to implement critical, utility back-up systems at City facilities and essential/emergency community facilities, including but not limited to microgrids, solar + storage, and other back-up, sustainable utility resources PW / Architectural Services
Amelia Feichtner
Future grant opportunities
Constrained by lack of current funding 2030
Protect life and property
Emergency services
Partnerships and
implementation
Policy 1.9
Policy 4.1
Policy 6.2
Tsunami Alerting System
Implement overhead paging at Santa Monica Pier with ability to provide tsunami alerts and evacuation directions. Complete assessment of other communications tools, such as, but not limited to digital kiosks and siren systems, to widely distribute tsunami education and imminent threat alerts and warnings along Santa Monica’s coastal areas. Regularly test communications systems during earthquake/tsunami preparedness events, like the annual California ShakeOut Drill, California Tsunami Awareness Week, and World Tsunami Awareness Day.

OEM, SMPD, CDD
Lindsay Call
Future grant opportunities
Constrained by staff availability and capacity
for implementation; Coastal Commission and
neighboring jurisdictions participation;
available funding
2027
Protect life and property
Emergency services
Public awareness
Public participation
Partnerships and
implementation
Policy 6.2
Policy 6.3
Natural Systems Improvement Projects
Natural Dune Restoration Expansion
To protect beaches and beach-front properties from erosion, sea level rise, and coastal flooding, continue to expand and maintain the Natural Dune Beach Restoration projects. By the end of 2029, the goal would be to have at least 50 acres of established beach dunes.

PW / OSE
Shannon Parry
Grants awarded to partner agencies
(Bay Foundation)
Constrained by approvals from outside
organizations (Coastal Commission, U.S. Fish &
Wildlife); staff capacity for maintenance;
community education
2029
Protect life and property
Public awareness
Public participation
Partnerships and
implementation
Natural systems
Policy 4.1
(Action 4.1.7)
Food Resilience Through Community Gardening
Increase production of food grown and donated from City-owned community gardens to local organizations to increase food resilience of vulnerable Santa Monica residents through the expansion of additional community garden space.

PW / OSE
Shannon Parry
Grants, park impact fees, CDBG funds
Finding suitable land available for the
expansion of the Community Garden program;
the need for additional staffing to properly
manage the expanded program
2029
Public awareness
Public participation
Partnerships and
implementation
Natural systems
Education and Awareness Programs
Inclusive Emergency Communications
Conduct emergency response, mitigation, and preparedness outreach in multiple languages to better reach diverse Santa Monica communities, including international tourists and persons with access and functional needs. Create standards for emergency response messaging to ensure it meets standards in City’s Language Access Administrative Instruction.

CMO / OEM, Administration
Lindsay Call
Private and state grant funding
Available funding, grant instability, available
staff capacity for implementation
2027
Emergency services
Public awareness
Public participation
Policy 6.3
Local Wildfire Safety Education
Develop education campaign on mandatory wildfire safety practices, such as defensible space standards and wildland urban interface building codes, required for areas of Santa Monica within the 2025 State-identified Very High Fire Hazard Severity Zones.

SMFD/ Fire Prevention
Joe Cavin
General fund, private/state grant funding
Available funding, grant instability 2027 Public awareness Public participation
Policy 2.1
Policy 6.2
Policy 6.3
City Readiness Initiatives
Expand Critical Emergency Management Technologies
Expand City GIS mapping, staffing, training, and tools to better facilitate emergency planning and response activities, including use of public education/communications. Expand on cloud infrastructure, data servers, and staffing to support the implementation, execution, and maintenance of critical technologies to support first responders. Continue adopting evacuation mapping technology to improve awareness of city evacuation zones, hazard areas, and assist with the prompt implementation of evacuation and shelter-in-place directions during emergencies.

ISD, CMO, SMFD, SMPD, PW
Lindsay Call.

Prasanna Joshi
General fund
Available funding, available staff capacity for
implementation
2028
Emergency Services
Public awareness
Public participation
Partnerships and
implementation
Policy 6.1

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ADDITIONAL RESOURCES HELPFUL DURING THE IMPLEMENTATION

PROCESS
As the City begins to implement the action items selected, they can further evaluate the benefit-cost analysis (BCA) of a specific action using the FEMA-provided Project Evaluation Worksheet included at the end of this section (Table 4-6). This worksheet is based on the “STAPLEE” process, whereby the benefits of a given proposed action are weighed against the costs of implementing it (see Tables 4-1 and 4-2). The data on these worksheets can help the RPC determine the most cost-effective mitigation solutions for the community.

Depending on the source of the funding used to implement these actions, some projects may need a more detailed BCA, but this worksheet provides a first-screening methodology.

FEMA also requires local governments to analyze the benefits and costs of a range of mitigation actions that can reduce the effects of each hazard within their community. BCA is used in hazard mitigation to evaluate whether the benefits to life and property protected through mitigation efforts exceed the cost of the mitigation activity. Conducting a BCA for a mitigation activity can assist communities in determining whether a project is worth undertaking now, in order to avoid disaster-related losses later. The analysis is based on calculating the frequency and severity of a hazard, avoided future damage, and risk.

The BCA review must be comprehensive to the extent that it can evaluate the monetary and non-monetary benefits and costs associated with each action. Thus, the BCA should at least consider the following questions:

1. How many people will benefit from the action?

2. How large is the area that would be impacted?

3. How critical are the facilities that benefit from the action?

4. Are there any environmental constraints associated with the action, and if so, is the overall benefit to the community greater than the environmental costs? Additional information regarding the BCA methodology and resources is provided in Appendix C.

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Table 4-6: Project Evaluation Worksheet
Jurisdiction: Contact:

Project Title Phone:

Agency: E-mail:

Hazard(s):

Flood Zone: Base Flood
Elevation:

Erosion Rate:

Critical Facility/Population At Risk:

Environmental Impact: Historic Preservation Impact:

High Medium Low High Medium Low
Importance to Protection of Life/Property and
Disaster Recovery
Risk of Hazard Impact:

High Medium Low High Medium Low
Estimated Cost: Project Duration:

Value of Facility: Value of Contents:

Source(s) of Financing:

Project Objectives:

Project Description:

Proposal Date:

Evaluation Category Considerations Comments
Social
Community Acceptance
Adversely Affects Segments of the
Population
Technical
Technical Feasibility
Long Term Solution
Secondary Impacts
Administrative
Staffing
Funding Allocated
Maintenance / Operations
Political
Political Support
Plan Proponent
Public Support
Legal Authority
Action Subject to Legal Challenge
Economic
Benefit
Cost of Action
Contributes to Economic Goals
Outside Funding Required
Environmental
Affects Land / Water Bodies
Affects Endangered Species
Affects Hazardous Materials and Waste
Sites
Consistent with Community
Environmental Goals
Consistent with Federal Laws

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SECTION 5: PLAN MAINTENANCE
The plan maintenance section of this document details the formal process that will ensure that this Hazard Mitigation Plan remains an active and relevant document. The plan maintenance process includes the following:

1. a schedule for monitoring and evaluating the Plan annually and producing a Plan revision every five years,

2. a description of how the City of Santa Monica will integrate public participation throughout the plan maintenance process, and

3. an explanation of how the City of Santa Monica intends to incorporate the mitigation strategies outlined in this Plan into existing planning mechanisms such as the City’s General Plan, Capital Improvement Plans, and Building and Safety Codes.

MONITORING AND IMPLEMENTING THE PLAN
Plan Adoption
City Council is responsible for adopting Santa Monica’s Local Hazard Mitigation Plan (Plan). This governing body has the authority to promote sound public policy regarding hazard mitigation.

Once the Plan is adopted, the City’s Chief Resilience Officer from the Office of Emergency Management will be responsible for submitting the Plan to the State Hazard Mitigation Officer at the Governor’s Office of Emergency Services. The Governor’s Office of Emergency Services will then submit the Plan to the Federal Emergency Management Agency (FEMA) for review. This review will address the federal criteria outlined in FEMA Interim Final Rule 44 CFR Part 201. Upon acceptance by FEMA, Santa Monica will gain eligibility for Hazard Mitigation Grant Program funds.

Coordinating Body
The Santa Monica Resilience Planning Committee will be responsible for coordinating implementation of the Plan’s action items and undertaking the formal review process. The City Manager, or designee, will assign representatives from City agencies, including, but not limited to, the current Resilience Planning Committee members. At this time, the Resilience Planning Committee consists of representatives from the following departments:
 City of Santa Monica Manager’s Office, Office of Emergency Management  City of Santa Monica Fire Department, Fire Prevention  City of Santa Monica Public Works Department, Administration  City of Santa Monica Public Works, Engineering and Street Services  City of Santa Monica Community Development Department, City Planning  City of Santa Monica Information Services Department, GIS The Resilience Planning Committee is supported by a larger body of advisors representing several other City departments, agencies and local community organizations that have a vested interest in managing or reducing the natural and human-made hazards in the city of Santa Monica. This larger body, referred to as the Hazard Mitigation Advisory Committee (Advisory Committee), has responsibility for reviewing the Plan and providing input on the action items proposed and their prioritization. The current Advisory Committee includes representatives from many local agencies

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and organizations in an effort to make this group as diverse as possible, bringing together people with differing skills, experiences, perspectives, and ideas. This diversity hopefully translates into thoughtful and comprehensive action items and policies. The agencies and organizations that are part of the Advisory Committee are listed below:

City of Santa Monica Departments
 City of Santa Monica Attorney’s Office
 City of Santa Monica Manager’s Office, Office of Emergency Management  City of Santa Monica Community Development Department, Building and Safety  City of Santa Monica Community Development Department, City Planning  City of Santa Monica Department of Transportation
 City of Santa Monica Finance Department
 Santa Monica Fire Department, Fire Administration
 Santa Monica Fire Department, Fire Prevention
 City of Santa Monica Housing and Human Services Department  City of Santa Monica Information Services Department
 City of Santa Monica Police Department
 City of Santa Monica Public Works Department, Administrative Services  City of Santa Monica Public Works Department, Engineering & Street Services  City of Santa Monica Public Works Department, Office of Sustainability and the Environment
 City of Santa Monica Public Works Department, Santa Monica Airport  City of Santa Monica Rent Control Department
Regional Government Partners
 City of Los Angeles, Emergency Management Department
 County of Los Angeles, Office of Emergency Management Local Educational Institutions
 Santa Monica College (SMC)
 Santa Monica-Malibu Unified School District (SMMUSD)
Local Hospitals
 University of California, Los Angeles (UCLA) Health/Santa Monica Medical Center  Providence Saint John’s Health Center
Local Non-Profits
 American Red Cross
 Westside Food Bank
Local Business Organizations
 Downtown Santa Monica Business Improvement District
 Santa Monica Chamber of Commerce
 Santa Monica Travel and Tourism
The Resilience Planning Committee will meet no less than bi-annually. Meeting dates will be scheduled once the final Plan has been adopted by City Council and approved by the appropriate

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FEMA office. These meetings will provide an opportunity to discuss the progress of the action items and maintain the partnerships that are essential for the sustainability of the Plan.

Convener
City Council will adopt Santa Monica’s Local Hazard Mitigation Plan, and the Resilience Planning Committee will take responsibility for Plan implementation. The City Manager, or designee, will serve as a convener to facilitate the meetings of the Resilience Planning and Advisory committees, and will assign tasks such as updating and presenting the Plan to the members of the committees.

Plan implementation and evaluation will be a shared responsibility among all of the Resilience Planning Committee members. Future updates of the Plan will require participation of the Advisory Committee.

Implementation through Existing Programs
The City of Santa Monica addresses statewide planning goals and legislative requirements through its General Plan, Capital Improvement Plans, and City Building and Fire Codes. The Local Hazard Mitigation Plan provides a series of recommendations, many of which are closely related to the goals and objectives of existing planning programs. The City of Santa Monica will have the opportunity to implement recommended mitigation action items through existing programs and procedures.

The City of Santa Monica Building and Safety Department, the City of Santa Monica Fire Department, the City of Santa Monica Public Works Department, and the City of Santa Monica Police Department are responsible for administering the Building and Fire Safety Codes, and other regulations designed to improve safety of the community, such as the policies in the Safety Element of the General Plan. In addition, the Resilience Planning Committee will work with other agencies at the state level to review, develop and implement Building and Fire Safety Codes that are adequate to mitigate or reduce the damage posed by natural and human-made hazards, with an emphasis on life-safety criteria for new construction and re-development of existing construction.

The goals and action items in Section 4 of the Plan may be achieved through activities recommended in the City's Capital Improvement Plans (CIP). Various City departments develop CIP plans and review them on an annual basis. Upon annual review of the CIPs, the Resilience Planning Committee will work with City departments to identify the action items that are consistent with CIP planning goals and integrate them where appropriate.

Within six months of formal adoption of the Plan, the recommendations listed above will be incorporated into the process of existing planning mechanisms at the City level. The meetings of the Resilience Planning and Advisory Committees will provide an opportunity for committee members to report back on the progress made on the integration of mitigation planning elements into City planning documents and procedures.

Economic Analysis of Mitigation Projects
FEMA's approaches to identify the costs and benefits associated with natural hazard mitigation strategies, measures, or projects, fall into two general categories: benefit/cost analysis and costeffectiveness analysis. Conducting a benefit/cost analysis for a mitigation activity can assist communities in determining whether a project is worth undertaking now, in order to avoid

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disaster-related damages later. Cost-effectiveness analysis evaluates how best to spend a given amount of money to achieve a specific goal. Determining the economic feasibility of mitigating natural hazards can provide decision-makers with an understanding of the potential benefits and costs of an activity, as well as a basis upon which to compare alternative projects.

Given federal funding, the Hazard Mitigation Advisory Committee will emphasize the use of a FEMA-approved benefit/cost analysis approach to identify and prioritize mitigation action items. A copy of a Project Evaluation Worksheet modeled after the STAPPLE cost benefit analysis process preferred by FEMA is included at the end of Chapter 4, and additional information regarding the economic analysis of mitigation action items is provided in Appendix C of the Plan. For other projects and funding sources, the Hazard Mitigation Advisory Committee may use other approaches to understand the costs and benefits of each action item and develop a prioritized list.

Of particular concern is that the action items implemented by the City result in the equitable allocation of resources that consider the socially vulnerable members of the community. The impact of the hazards identified on priority populations at the census-tract level was qualitatively addressed in several sections of this document, but quantitative modeling tools that will allow for a better characterization of hazard outcomes among differing social and economic groups are expected to become more common. Future updates of this Plan should consider the use of these modeling tools as they become mainstream, following rigorous peer-review.

EVALUATING AND UPDATING THE PLAN
Formal Review Process
The City of Santa Monica Local Hazard Mitigation Plan will be evaluated on an annual basis to determine the effectiveness of the programs and action items, and to identify changes in land development or programs that may affect mitigation priorities. The evaluation process includes a firm schedule and time line, and identifies the local agencies and organizations participating in the evaluation of the Plan. The City’s Chief Resilience Officer will be responsible for contacting the Resilience Planning Committee members and organizing the annual meeting. Committee members will be responsible for monitoring and evaluating the progress of the mitigation strategies in the Plan.

The Committee will review the goals and action items to determine their relevance to changing situations in the City, as well as changes in State or Federal policy, and to ensure they are addressing current and expected conditions. The Committee will also review the risk assessment portion of the Plan to determine if this information should be updated or modified given new available data. The coordinating organizations responsible for the various action items will report on the status of their projects, the success of various implementation processes, difficulties encountered, success of coordination efforts, and which strategies should be revised. These annual reviews will also allow the City and individual departments and organizations to assess whether a given action item needs to be updated or modified, or whether the implementation of a given action should be extended or postponed to the next Plan update.

The convener will assign the duty of updating the Plan to one or more of the Resilience Planning Committee members. The designated committee members will have three months to make appropriate changes to the Plan before submitting it to the Hazard Mitigation Advisory Committee members, and presenting it to City Council. The Resilience Planning Committee will also notify all

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holders of the Plan when changes have been made. Every five years the updated Plan will be submitted to the State Hazard Mitigation Officer and the Federal Emergency Management Agency for review.

Continued Public Involvement
The City of Santa Monica is dedicated and committed to involving the public directly in review and updates of the Local Hazard Mitigation Plan. The public will be encouraged to and provided with the opportunity to give feedback on the Plan. Copies of the Plan will be kept at the front desk of City Hall, and at City libraries. The Plan will also be placed on the City’s website for review by the public, or alternatively, the existence and location of copies of the Plan will be publicized on the City’s website and newsletters. In addition, information on how to obtain copies of the Plan and any proposed changes will be posted on the City’s website. This site will list an e-mail address and phone number to which people can direct their comments and concerns.

A public meeting will also be held after each annual evaluation or when deemed necessary by the Hazard Mitigation Advisory Committee. The meetings will provide the public with a forum at which they can express their concerns, opinions, or ideas about the Plan. The City’s Public Information Officer will be responsible for using City resources to publicize the annual public meetings and maintain public involvement through the City’s public access channel, web page, and newspapers or newsletters.

PROGRESS MADE SINCE ADOPTION OF THE 2016 PLAN
The Santa Monica is and has been committed to reducing the impact that natural and humanmade hazards can have on its residents, businesses, infrastructure, and critical and essential facilities. With adoption of the City’s 2016 Disaster Mitigation Plan, several goals and action items were identified and targeted for implementation. Those action items that were implemented and completed during the 2016-2024 timeframe, or that are currently being implemented are listed in Table 5-1 below. New item actions that were identified as part of this 2025 Plan Update are discussed and listed in Section 4.

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ACTION # IN
2016 PLAN ACTION ITEM STATUS
Action 1 Identify and pursue potential
projects and funding sources to
develop and implement local and
county mitigation activities.

The City of Santa Monica has applied for and received several grants to improve hazard mitigation since 2016. Highlights include:
• Santa Monica Retrofit Funding: Santa Monica was awarded a $6.7 million federal grant from FEMA to assist multi-family residential soft-story building owners with a portion of financial funding for seismic retrofit design and construction costs. santamonica.gov - Seismic Retrofit Program
• Zero Emission Backup Generators: Santa Monica obtained funding for emergency backup generators for City facilities that have been identified as having a critical community-facing emergency response purpose, such as public shelters or family assistance centers. Cal OES Clean Power Resiliency grant funding provided $291,611 to this project. FY20 Community Power Resiliency Legislative Report • Pier Bridge Replacement Project: After several years, Santa Monica obtained grant funding to complete the retrofit of the Santa Monica Pier Bridge, the primary transportation access to Santa Monica Pier. The original bridge was built in 1939, and when structurally assessed, received an 8.2 out of 100 on a seismic sufficiency scale. As a result, renovation of this bridge is a major retrofit priority for the City. The City obtained over $25 million in federal Highway Bridge Program funding to complete renovations. The retrofit project is expected to commence in the fall of 2025. santamonica.gov - Pier Bridge Replacement Project
• Public Works Microgrid Feasibility Study: Electric Program Investment Charge (EPIC) funding allowed for the Santa Monica Public Works Department to conduct a City Yards microgrid feasibility study. This study laid the foundation to determine the benefits of a microgrid to reduce energy demand and improve disaster resiliency during a power event. Final Project Report, Santa Monica City Yards Advanced Energy District • Drought-Resiliency Water System Improvements: The City obtained $10 million through Prop 1 Water Desalination Grant Program to upgrade the City’s Arcadia Water Treatment Plant and construct a new Olympic Advanced Water Treatment Facility.

These facilities will expand groundwater production and allow the City to continue to work towards self-sufficiency. santamonica.gov - New Water Project Takes Landmark Step Toward Water Self-Sufficiency
Action 2 Integrate the Local Hazard
Mitigation Plan (LHMP) into existing
programs, ordinances, building
codes. Integrate the goals and action
Hazards identified in the 2016 LHMP have been addressed through city programs and ordinances to reduce hazard vulnerability in Santa Monica.

Some key projects and plans include:

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ACTION # IN
2016 PLAN ACTION ITEM STATUS
items from the LHMP into existing
regulatory documents and
programs, including local
ordinances and building codes,
where appropriate.
• Seismic Retrofit Ordinance: Adopted in 2017 to implement a Seismic Retrofit Program for the City of Santa Monica. The program identified over 2,000 commercial and multifamily residential structures that were potentially seismically vulnerable and potentially requiring structural improvement. As of June 2025, 65% of all identified buildings had completed their retrofit or demonstrated compliance, with 67% of soft-story multifamily residential structures completed. santamonica.gov - Seismic Retrofit Program Building Type Qty.

Noticed
Number
Closed
Number
Remaining
Open
Retrofit
Completion
Due Date
Cases
Sent to Code
Enforcement
Tilt-Up 42 24 (57%) 18 Aug. 2020 14
URM 93 77 (83%) 16 Aug. 2019 17
Soft-Story 1,688 1127 (67%) 561 Sep. 2025 –
July 2026 0
Non-Ductile
Concrete 66 39 (59%) 27 Oct. 2027 17
Steel Moment
Frame 80 15 (19%) 65 Oct. 2037 0
TOTALS 1,969 1,282 (65%) 687 48
• Eco-Friendly Public Building Design & Implementation:
o Santa Monica’s new City Hall East building was completed in 2020. This is one of the greenest buildings in the world and the first municipal building to receive Living Building Challenge Certification from the International Living Future Institute, which means this building is Net Zero Water, Net Zero Energy Building, Net Zero Waste, and takes out 20 worst-in-class chemicals prevalent in the business industry. The building features robust solar panels, composting toilets, passive survivability design concepts and is the first building in California to convert rain-to potable water on site. Through the City’s design and use of this building, Santa Monica hopes to set an environmentally responsible example for local architects and municipalities.
o The City Yards Modernization Project, which occurred mostly between 2019 and

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ACTION # IN
2016 PLAN ACTION ITEM STATUS
2022, realizes the feasibility study conducted using grant funding. The project embeds sustainability, hazard mitigation, and operational resilience into public works infrastructure required to support daily City operations. The redesigned site includes a 609kW rooftop solar array integrated with two 803kW Tesla Megapack batteries forming a microgrid that provides energy back-up power to all new buildings, including the City’s Fire Training facility. Portions of the site are built on a former landfill; as a result, extensive soil stabilization and methane mitigation measures were taken. Long-term foundation issues were addressed by supporting the roadways and buildings with concrete piles driven into bedrock beneath the landfill. Additionally, the new buildings take advantage of Santa Monica’s purple pipe system, using reclaimed and treated water for toilet flushing, fleet vehicle washing, and irrigation to reduce potable water use. • Coastal Bluffs Monitoring & Removal Work: In 2023 and 2024, extensive geotechnical and monitoring activities were carried out along the Santa Monica Bluffs. The City’s geotechnical consultant completed a detailed field mapping survey and conducted updated topographic and aerial photography surveys using unmanned aerial vehicles to document bluff features and compare them with past conditions. These efforts resulted in an updated geotechnical study and a comprehensive maintenance and monitoring report.
o The geotechnical study focused on evaluating the overall surface conditions of the bluffs and developing a priority list and action plan for future maintenance. This work included reviewing historical reports, aerial imagery, and geologic data; conducting oblique aerial photography surveys; performing visual inspections of bluff features; and summarizing the condition of drains and monitoring wells, as well as analyzing slope instability mechanisms.
o The maintenance report assessed the current condition of horizontal drains and monitoring wells, provided monitoring recommendations, and outlined maintenance procedures for both existing and future drains. o Based on monitoring of the condition of the Santa Monica bluffs, a stabilization project was undertaken in July 2023 to remove an unstable portion of the bluffs just above Pacific Coast Highway (PCH) between the California Incline and northbound on-ramp to Moomat Ahiko Way. The cracked block of sediment, which likely formed due to the intense rains that had occurred in December 2022-January 2023, was at risk of separating. Removal action was taken to ensure

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ACTION # IN
2016 PLAN ACTION ITEM STATUS
vehicle traffic and safety on PCH.
• Climate Change Actions: The City adopted several plans that further define its goals towards resiliency and sustainability, and of mitigating disaster impacts. These plans include:
o 2017 City’s Water Neutrality Ordinance that caps water use for new developments to the historical five-year average for the site. o 2019 Climate Action Plan that sets a goal for the city to reduce carbon emissions 80% by 2030. The plan enhances resilience to climate change by building a climate-ready community that aims to be water self-sufficient, prepared for coastal flooding, and focuses on low carbon food systems and ecosystems. o 2020 Urban Water Management Plan that incorporates a water shortage contingency plan for multi-year drought conditions.
• Drought Mitigation & Water Sustainability: In 2022-2023, Santa Monica implemented its Sustainable Water Infrastructure Project that provides a drought-resistant water supply for the city. The project produces up to 1,680 acre-feet per year of advanced treated recycled water for approximately 10% of the city’s water supply. santamonica.gov - Sustainable Water Infrastructure Project (SWIP) • Climate Change Prevention: In 2024, Santa Monica passed a Low Carbon Concrete Ordinance (#2778) that reduces emissions from concrete poured in new buildings, spas, and swimming pools to reduce the greenhouse gas emissions from the construction project. Compliance with the ordinance is achieved by demonstrating that the concrete used meets the cement limit or the global warming potential limit. santamonica.gov - Low-Carbon Concrete Requirements

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ACTION # IN
2016 PLAN ACTION ITEM STATUS
• Water and Wastewater Infrastructure Seismic Upgrades: The City’s Water Resources Division has been incorporating seismic upgrades to its water and wastewater infrastructure through its annual replacement programs. The annual water and wastewater main replacement program replaces, on average, 1-2 miles of pipelines each year. Restraint joints are included where necessary to enhance seismic resiliency and earthquake-resistant pipes are considered in areas where the pipeline may cross fault lines. The new Olympic Transmission Main uses earthquake resistant pipes over areas where it crosses fault lines to deliver groundwater to the Olympic Advanced Water Treatment Facility that is co-located at the Arcadia Water Treatment Plant. In addition, the Water Resources Division updates its water and wastewater master plans every 5 years where it updates/calibrates its hydraulic model and identifies vulnerable areas that may be impacted by seismic events.
• 4th Street Overpass Seismic Upgrades: Analysis of water and wastewater pipeline on 4th Street at the I-10 Freeway overpass determined the section of pipe in question would not cause service interruptions if it were to fail. Should the pipe along the overpass alignment fail, the City would be able to isolate it and continue to provide water and wastewater service, including max day and fire flow conditions, to its customers on either side of the overpass without any issues.

Action 3 Design and implement a protection
program for the critical information
systems infrastructure, including
telephones, computers, radio, 911
services, information systems and
backup systems.
• Consolidated Public Safety Communications Center: In 2015, Santa Monica launched a consolidated 911 dispatch center that handles all local Police, Fire, and Emergency Medical Services emergency call answering and radio dispatch services for Santa Monica. Multi-departmental incidents are managed by dispatchers who are crosstrained in multiple public safety dispatching skillsets. The Public Safety Communications Center is a part of the City’s Office of Emergency Management (OEM), ensuring prompt notification of emergency managers during escalating incidents and the integration of dispatch leadership into the City’s Emergency Operations Center. • Dispatch Technology Improvements: Since 2016, Santa Monica has adopted several public safety technology improvements. In 2017, Los Angeles County and the City of Santa Monica implemented “Text to 911” where mobile users can report emergencies and communicate with dispatchers using text messages. In 2024, Santa Monica OEM, Police and Fire implemented a new cloud-based computer-aided dispatch (CAD) system to improve emergency response operations and situational awareness. During the launch of CAD, Santa Monica launched technology to automatically update callers with Police service requests via text message.

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ACTION # IN
2016 PLAN ACTION ITEM STATUS
• Workplace and Emergency Response Flexibility: In 2020, Santa Monica augmented its remote-based technology, allowing more employees to work from home or off-site locations. The City deployed laptops to personnel across the organization and implemented web-based collaboration and document storage tools. The shift to remotebased workspaces has greatly improved the ability for emergency response functions to occur in non-traditional or back-up locations.
• GIS Disaster Management Activities: During the COVID-19 pandemic and Los Angeles Marathon, GIS surveying tools and dashboards were utilized heavily to collect field reports, create situational analysis tools for the Emergency Operations Center and leadership, and share data and resources with the general community. Community hazard and tsunami evacuation maps are created in ArcGIS and available for the public.
• Improved Map-Based Assessment Tools: In 2023, Santa Monica implemented webbased software to collect and map damage and safety assessment data. This tool was tested during a 2024 full-scale disaster exercise with Cal OES Safety Assessment Program. The City of Santa Monica maintains a web-based incident management tool to maintain its disaster inventory and collect incident documentation. • Future Technology Adoption Plans: As of 2025, the City is in the early stages of fully adopting evacuation mapping technology, in alignment with LA County and other regional municipalities. The launch of this technology, in alignment with the adoption of a citywide evacuation plan, will improve awareness of city evacuation zones, hazard areas, and assist with prompt implementation of evacuation and shelter-in-place directions during emergencies.

Action 4 Design and implement a
comprehensive campaign of public
awareness and preparedness of local
natural hazards, using media, print,
radio, and the internet.

Household Disaster Kit Education: In 2016, the City launched a large public-education campaign on general disaster preparedness called “I’ve Got 7,” in partnership with the local American Red Cross chapter. The campaign educated the community on the types of hazards that could impact Santa Monica and emphasized that the community needs sevendays of supplies in seven categories. After several years, the campaign concluded and updated disaster kit information is distributed at community events. • OEM Public Education: Santa Monica OEM continues to make the public aware of local hazards and preparedness needs. Santa Monica launched a new website with several emergency preparedness and hazard information webpages. OEM regularly shares preparedness and mitigation information using social media and in-person learning opportunities. In 2023, Santa Monica maintained its designation of a TsunamiReady® community, meeting public education requirements.

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ACTION # IN
2016 PLAN ACTION ITEM STATUS
• Community Emergency Response Team (CERT) Training: The City’s OEM has offered CERT training courses to local residents and business employees. CERT is a national, research-validated training program that trains participants in basic disaster response skills like fire safety, light search and rescue, and disaster medical operations. Since 2016, over 550 community members have received CERT training, with the City typically offering the course twice a year for 25 people.

Action 5 Continue to strengthen and develop
evacuation plans, policies, and
procedures for City facilities located
throughout Santa Monica.
• City Facility Evacuation Plans: The City of Santa Monica has Emergency Action Plans for every employee worksite, with the most recently updated plans dating from 2022.

The Emergency Action Plans include detailed facility evacuation plans and hazardspecific response procedures, such as those for earthquakes, tsunamis, and hazardous materials spills. Plans include directions for those with access and functional needs, such as those with visual or mobility disabilities. Evacuation drills are held regularly, overseen by the City’s Safety Officer.
• Pier Emergency Plan: In 2019, OEM worked with SMPD, SMFD, and Santa Monica City departments and Pier stakeholders to create the Pier Emergency Response Plan. The plan details emergency evacuation, repopulation, and crisis communications activities.

The plan also provides checklists to Pier businesses to respond to emergency scenarios including thunderstorms, tsunami, and large-scale criminal incidents.

Action 6 Enhance capability of alert system of
a public alert and notification system
for disasters.
• Non-Traditional Disaster Response Communications: During the COVID-19 emergency, Santa Monica utilized non-conventional communication means to share information with the public, including postcards sent to every household and flyers distributed in grocery bags.
• Local Alert & Warning: Santa Monica’s mass notification system, SMAlerts, is a robust alerting platform that has the capability of alerting the community of emergency information. The system was upgraded in 2022 to include three levels of emergency alerting:

1. General public safety messages to users who enrolled via santamonica.gov/alerts

2. Emergency messages to residents and businesses within a geographic area using E911 data

3. Wireless Emergency Alerting (WEA) to all individuals within a geographic area • City Crisis Communications Plan: The City has also implemented a crisis communications plan that identifies other forms of emergency communications systems that can be used during a disaster, including multiple social media platforms, digital kiosk message boards, the City’s website, and a disaster hotline.

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Packet Pg. 828 Attachment: 2025 SM LHMP Volume 1: Mitigation Action Plan [Revision 1] (7378 : Local Hazard Mitigation 2025-2030
Local Hazard Mitigation Plan
Prepared in collaboration with:
1642 E. Fourth Street,
Santa Ana, California
www.earthconsultants.com

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Packet Pg. 829 Attachment: 2025 SM LHMP Volume 2: Hazards [Revision 1] (7378 : Local Hazard Mitigation Plan Update) 2025-2030
Local Hazard Mitigation Plan
Volume II: Hazards

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Packet Pg. 830 Attachment: 2025 SM LHMP Volume 2: Hazards [Revision 1] (7378 : Local Hazard Mitigation Plan Update) Local Hazard Mitigation Plan
City of Santa Monica, California
2025 Table of Contents – Volume II Page i

TABLE OF CONTENTS
SECTION ......................................................................................... PAGE # VOLUME I: MITIGATION ACTION PLAN
Executive Summary
Resumen Ejecutivo
Section 1: Introduction
Section 2: Community Profile
Section 3: Risk Assessment
Section 4: Goals and Mitigation Actions
Section 5: Plan Maintenance
VOLUME II: HAZARDS
Section 6: Earthquakes
WHY ARE EARTHQUAKES A THREAT TO THE CITY OF SANTA MONICA? ................................................................. 6-1 EARTHQUAKE BASICS – DEFINITIONS ................................................................................................................ 6-3 CAUSES OF EARTHQUAKE DAMAGE .................................................................................................................. 6-7 HISTORY OF EARTHQUAKE EVENTS IN SOUTHERN CALIFORNIA ............................................................................ 6-9 Unnamed Earthquake of 1769............................................................................................................ 6-10 Wrightwood Earthquake of December 12, 1812................................................................................. 6-10 Unnamed Earthquake of December 21, 1812..................................................................................... 6-13 Unnamed Earthquake of 1855............................................................................................................ 6-13 Santa Monica Earthquake of 1930 ...................................................................................................... 6-13 Long Beach Earthquake of 1933 ......................................................................................................... 6-13 Torrance-Gardena Earthquakes of 1941 ............................................................................................. 6-14 San Fernando (Sylmar) Earthquake of 1971 ........................................................................................ 6-14 Point Mugu Earthquake of 1973 ......................................................................................................... 6-15 Malibu Earthquake of 1979 ................................................................................................................ 6-15 Whittier Narrows Earthquake of 1987................................................................................................. 6-15 Malibu Earthquake of 1989 ................................................................................................................ 6-16 Landers and Big Bear Earthquakes of 1992 ......................................................................................... 6-16 Northridge Earthquake of 1994........................................................................................................... 6-16 Hector Mine Earthquake of 1999........................................................................................................ 6-17 Baja California Earthquake of 2010 .................................................................................................... 6-17 Ridgecrest Earthquake Sequence of 2019 ........................................................................................... 6-18 Ojai Earthquake of 2023..................................................................................................................... 6-18 EARTHQUAKE HAZARD ASSESSMENT............................................................................................................... 6-18 Choosing Earthquakes for Planning and Design.................................................................................. 6-18 Seismic Shaking.................................................................................................................................. 6-19 Seismic Shaking Sources ................................................................................................................. 6-22 Surface Fault Rupture ......................................................................................................................... 6-37 Definitions and Statutory Requirements........................................................................................... 6-37 Santa Monica Fault Zone................................................................................................................. 6-39 Liquefaction and Related Ground Failure ........................................................................................... 6-44 Definitions....................................................................................................................................... 6-44 Liquefaction Susceptibility In and Near Santa Monica..................................................................... 6-46 Seismically Induced Slope Failure ...................................................................................................... 6-46

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City of Santa Monica, California
2025 Table of Contents – Volume II Page ii
TABLE OF CONTENTS (continued)
SECTION ......................................................................................... PAGE # VULNERABILITY ASSESSMENT ......................................................................................................................... 6-47 Vulnerable Structure Types................................................................................................................. 6-48 Unreinforced Masonry Buildings..................................................................................................... 6-48 Soft-Story Buildings ......................................................................................................................... 6-49 Wood-Frame Structures................................................................................................................... 6-49 Pre-Cast Concrete Structures ........................................................................................................... 6-49 Reinforced Masonry Tilt-up Buildings ............................................................................................. 6-50 Reinforced Concrete-Frame Buildings ............................................................................................. 6-50 Multi-Story Steel-Frame Buildings.................................................................................................... 6-51 Mobile Homes ................................................................................................................................ 6-51 Other Conditions that Can Lead to Structural Failure.......................................................................... 6-52 Building Shape ................................................................................................................................ 6-52 Pounding......................................................................................................................................... 6-52 Critical Facilities and Infrastructure..................................................................................................... 6-52 RISK ANALYSIS............................................................................................................................................. 6-54 HazUS................................................................................................................................................ 6-54 HazUS Earthquake Scenarios for the Santa Monica Area.................................................................... 6-59 Building Damage ............................................................................................................................ 6-61 Total Economic Losses: Sum of Building-Related and Lifeline-Related Losses ................................ 6-69 Casualties........................................................................................................................................ 6-71 Damage to Critical and Essential Facilities ...................................................................................... 6-74 Utility Systems Damage................................................................................................................... 6-75 Fire Following Earthquake ............................................................................................................... 6-77 Debris Generation........................................................................................................................... 6-78 SEISMIC HAZARD MITIGATION ACTIVITIES ....................................................................................................... 6-79 Existing Mitigation Activities............................................................................................................... 6-79 California Earthquake Mitigation Legislation ................................................................................... 6-79 City of Santa Monica Codes ............................................................................................................ 6-80 Businesses/Private Sector................................................................................................................. 6-80 Hospitals......................................................................................................................................... 6-81 Earthquake Education ......................................................................................................................... 6-82 EARTHQUAKE RESOURCE DIRECTORY ............................................................................................................. 6-83 Local and Regional Resources ............................................................................................................ 6-83 State Resources................................................................................................................................... 6-83 Federal and National Resources ......................................................................................................... 6-84 Publications........................................................................................................................................ 6-85 Section 7: Tsunamis
WHY ARE TSUNAMIS A THREAT TO THE CITY OF SANTA MONICA? ....................................................................... 7-1 TSUNAMI BASICS – DEFINITIONS AND CAUSES ................................................................................................... 7-2 What is a Tsunami?............................................................................................................................... 7-2 What Causes a Tsunami?...................................................................................................................... 7-3 HISTORICAL, LOCALLY SIGNIFICANT TSUNAMIS.................................................................................................. 7-5 Santa Barbara Tsunami of 1812 .......................................................................................................... 7-10 Tsunami of May 10, 1877................................................................................................................... 7-10 Tsunami of April 13, 1923.................................................................................................................. 7-11 Earthquake and Tsunami of August 31, 1930...................................................................................... 7-11 Possible Tsunami of August 21, 1934 ................................................................................................. 7-11

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City of Santa Monica, California
2025 Table of Contents – Volume II Page iii
TABLE OF CONTENTS (continued)
SECTION ......................................................................................... PAGE # Aleutian Islands Tsunami of March 9, 1957........................................................................................ 7-11 Chilean Tsunami of May 23, 1960...................................................................................................... 7-12 Good Friday (March 28) Earthquake Tsunami of 1964........................................................................ 7-12 Boxing Day (December 26) Earthquake and Tsunami of 2004............................................................ 7-12 Chilean Earthquake and Tsunami of February 27, 2010...................................................................... 7-13 Tohoku, Japan Earthquake and Tsunami of March 11, 2011............................................................... 7-13 Tonga Volcanic Eruption and Tsunami of January 15, 2022 ............................................................... 7-14 TSUNAMI HAZARD ASSESSMENT FOR SANTA MONICA ...................................................................................... 7-14 Hazard Identification.......................................................................................................................... 7-14 Vulnerability and Risk ........................................................................................................................ 7-19 Risk Assessments - Methodology ........................................................................................................ 7-20 Risk Assessments - Results .................................................................................................................. 7-20 TSUNAMI MITIGATION ACTIVITIES .................................................................................................................. 7-24 TSUNAMI RESOURCE DIRECTORY ................................................................................................................... 7-27 City Resources.................................................................................................................................... 7-27 County Resources............................................................................................................................... 7-27 State Resources................................................................................................................................... 7-28 Federal Resources and Programs ........................................................................................................ 7-29 Publications........................................................................................................................................ 7-29 Section 8: Flood Hazards
WHY ARE FLOODS A THREAT TO THE CITY OF SANTA MONICA? .......................................................................... 8-1 HISTORY OF FLOODING IN THE CITY OF SANTA MONICA.................................................................................... 8-4 Historic Flooding in Los Angeles County .............................................................................................. 8-5 WHAT FACTORS CREATE FLOOD RISK? ............................................................................................................. 8-8 Climate................................................................................................................................................. 8-8 Geography and Geology .................................................................................................................... 8-13 Built Environment............................................................................................................................... 8-14 STORM FLOODING CHARACTERISTICS............................................................................................................. 8-14 Coastal Flooding................................................................................................................................. 8-14 Fluvial (Riverine) Flooding.................................................................................................................. 8-15 Pluvial (Urban) Flooding..................................................................................................................... 8-15 HOW FLOOD-PRONE AREAS ARE IDENTIFIED................................................................................................... 8-16 Flood Terminology ............................................................................................................................. 8-16 Floodplain....................................................................................................................................... 8-16 Floodway ........................................................................................................................................ 8-16 Flood Fringe .................................................................................................................................... 8-16 100-Year Flood ............................................................................................................................... 8-17 Development................................................................................................................................... 8-17 Base Flood Elevation (BFE) .............................................................................................................. 8-17 Special Flood Hazard Area (SFHA).................................................................................................. 8-17 Flood Mapping Methods, Products and Programs............................................................................... 8-17 Flood Insurance Rate Maps and Flood Insurance Studies ................................................................ 8-17 Mapped Flood Areas Outside of the 100-Year Flood Zone.............................................................. 8-20 Community Rating System............................................................................................................... 8-20 Risk Mapping, Assessment and Planning (Risk MAP) Program......................................................... 8-20 FLOOD HAZARD ANALYSIS FOR THE SANTA MONICA AREA............................................................................... 8-21 INUNDATION DUE TO CATASTROPHIC FAILURE OF WATER STORAGE STRUCTURES............................................... 8-25

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City of Santa Monica, California
2025 Table of Contents – Volume II Page iv
TABLE OF CONTENTS (continued)
SECTION ......................................................................................... PAGE # Flooding Due to Dam Failure ............................................................................................................. 8-25 Flooding Due to Failure of Above-Ground Water Storage Tanks ........................................................ 8-29 HAZARD ASSESSMENT................................................................................................................................... 8-30 Hazard Identification.......................................................................................................................... 8-30 Flood Hazard Mapping and Flooding Potential in the City of Santa Monica ....................................... 8-30 Urban Flooding and Existing Flood Protection Measures in the City of Santa Monica......................... 8-31 Inundation Due to Catastrophic Failure of Water Storage Structures................................................... 8-32 Water-Retaining Structures In and Near Santa Monica .................................................................... 8-32 Water Tank Failure Impacts............................................................................................................. 8-35 Stone Canyon Reservoir .................................................................................................................. 8-36 VULNERABILITY ASSESSMENT – COMMUNITY FLOOD ISSUES .............................................................................. 8-38 What is Susceptible to Damage During a Flood Event?....................................................................... 8-39 100-Year Coastal Flood Event.......................................................................................................... 8-39 Stone Canyon Inundation Event....................................................................................................... 8-39 RISK ANALYSIS............................................................................................................................................. 8-40 General Building Stock Exposure and Potential Building-Related Losses ............................................ 8-41 100-Year Coastal Flood Event.......................................................................................................... 8-41 Stone Canyon Inundation Event....................................................................................................... 8-42 Essential Facility Damage ................................................................................................................... 8-44 Induced Flood Damage: Debris Generation ....................................................................................... 8-45 Social Impact: Shelter Requirements................................................................................................... 8-45 Business and Industry ......................................................................................................................... 8-46 Public Infrastructure ........................................................................................................................... 8-46 FLOOD MITIGATION ACTION ITEMS ............................................................................................................... 8-46 FLOOD RESOURCE DIRECTORY ...................................................................................................................... 8-48 County Resources............................................................................................................................... 8-48 State Resources................................................................................................................................... 8-48 Federal Resources and Programs ........................................................................................................ 8-48 Other National Resources................................................................................................................... 8-49 Publications........................................................................................................................................ 8-52 Section 9: Landslides
WHY ARE LANDSLIDES A THREAT TO THE CITY OF SANTA MONICA? ..................................................................... 9-1 Physiographic Setting ........................................................................................................................... 9-1 Geologic Setting ................................................................................................................................... 9-2 DEFINITIONS ................................................................................................................................................. 9-6 What is a Landslide?............................................................................................................................. 9-6 What is a Debris Flow?......................................................................................................................... 9-6 CONDITIONS CONDUCIVE TO SLOPE FAILURES .................................................................................................. 9-7 Natural Conditions ............................................................................................................................... 9-7 Impacts of Development and Redevelopment ...................................................................................... 9-8 Alterations to Drainage and Groundwater Systems............................................................................... 9-8 Changes in Vegetation.......................................................................................................................... 9-9 HISTORICALLY AND LOCALLY SIGNIFICANT SOUTHERN CALIFORNIA LANDSLIDES ................................................... 9-9 1956 Portuguese Bend Landslide, Palos Verdes.................................................................................. 9-10 1969 Glendora, Los Angeles County .................................................................................................. 9-10 1977-1978 Monterey Park, Baldwin Hills and Repetto Hills, Los Angeles County.............................. 9-10 1978 Bluebird Canyon, Orange County.............................................................................................. 9-10

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City of Santa Monica, California
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TABLE OF CONTENTS (continued)
SECTION ......................................................................................... PAGE # 1979 Big Rock, Los Angeles County ................................................................................................... 9-10 1980 Southern California Landslides .................................................................................................. 9-10 1978-1979, 1980 San Diego County .................................................................................................. 9-11 1983 San Clemente, Orange County .................................................................................................. 9-11 1983 Big Rock Mesa, Malibu, Los Angeles County............................................................................. 9-11 1994 Northridge Earthquake Landslides ............................................................................................. 9-11 1995 Los Angeles and Ventura Counties Landslides........................................................................... 9-11 2003-Present Del Mar Bluff Stabilization, San Diego County ............................................................. 9-11 2005 La Conchita Landslide, Ventura County..................................................................................... 9-12 2005 Blue Bird Canyon Landslide, Laguna Beach, Orange County .................................................... 9-12 2018 Montecito Landslide, Santa Barbara County .............................................................................. 9-12 2021-2023 San Clemente Landslides, Orange County........................................................................ 9-12 2023 Rolling Hills Estates Landslide, Los Angeles County................................................................... 9-13 2023 Santa Monica Bluff Stabilization Emergency Work, Los Angeles County ................................... 9-13 LANDSLIDE HAZARD ASSESSMENT FOR SANTA MONICA.................................................................................... 9-13 Hazard Identification.......................................................................................................................... 9-13 Vulnerability and Risk ........................................................................................................................ 9-16 SUMMARY OF COMMUNITY LANDSLIDE ISSUES ................................................................................................ 9-18 What is Susceptible to Landslides?...................................................................................................... 9-18 Landslide Mitigation Activities............................................................................................................ 9-19 LANDSLIDE RESOURCE DIRECTORY................................................................................................................. 9-21 City Resources.................................................................................................................................... 9-21 County Resources............................................................................................................................... 9-21 State Resources................................................................................................................................... 9-21 Federal Resources and Programs ........................................................................................................ 9-22 Publications........................................................................................................................................ 9-22 Section 10: Wildfires and Urban Fires
WHY ARE FIRES A THREAT TO THE CITY OF SANTA MONICA?.............................................................................10-1 WILDFIRES ..................................................................................................................................................10-1 What are Wildfires?............................................................................................................................10-1 Wildfire Causes ..................................................................................................................................10-2 History of Wildfires Near Santa Monica and In Southern California ...................................................10-4 Topanga Canyon or Santa Monica Mountains Fire of 1938 .............................................................10-7 Bel Air, Brentwood and Santa Ynez Fires of 1961 ...........................................................................10-8 Los Angeles Fires of 1978................................................................................................................10-8 Tunnel Fire of 1991 (Oakland Firestorm).........................................................................................10-9 Laguna Fire of 1993 ......................................................................................................................10-10 Southern California Fires of 2003, Including Cedar Fire ................................................................10-10 Tubbs Fire of 2017 ........................................................................................................................10-11 Camp Fire of 2018 ........................................................................................................................10-12 Woolsey Fire of 2018 ....................................................................................................................10-13 Franklin (Malibu) Fire of 2024.......................................................................................................10-14 Palisades Fire of 2025 ...................................................................................................................10-14 Eaton Fire of 2025 .........................................................................................................................10-17 Wildfire Characteristics ....................................................................................................................10-17 Wildfire Hazard Identification ..........................................................................................................10-21 Federal Responsibility Areas (FRAs)...............................................................................................10-21

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City of Santa Monica, California
2025 Table of Contents – Volume II Page vi
TABLE OF CONTENTS (continued)
SECTION ......................................................................................... PAGE # State Responsibility Areas (SRAs)...................................................................................................10-22 Local Responsibility Areas (LRAs)..................................................................................................10-23 Mapped Wildfire Hazard Zones Near and In Santa Monica..............................................................10-23 STRUCTURE FIRES.......................................................................................................................................10-27 Definition and Recent Statistics ........................................................................................................10-27 Causes of Structure Fires...................................................................................................................10-28 Factors that Impact Structure Fire Risk in a Community ....................................................................10-29 Fires After an Earthquake ..................................................................................................................10-31 VULNERABILITY AND RISK ASSESSMENT .........................................................................................................10-33 What is Susceptible to Wildfires in Santa Monica.............................................................................10-33 Structure Fires...................................................................................................................................10-35 Fires After an Earthquake ..................................................................................................................10-37 Social Vulnerability to Fires..............................................................................................................10-38 FIRE HAZARD MITIGATION ACTIVITIES ..........................................................................................................10-43 Fire Prevention ................................................................................................................................. 10-43 Vegetation Management...................................................................................................................10-44 Construction Requirements...............................................................................................................10-45 Public Awareness .............................................................................................................................10-47 FIRE HAZARDS RESOURCE DIRECTORY..........................................................................................................10-51 Local Resources................................................................................................................................10-51 Santa Monica Fire Department......................................................................................................10-51 Automatic and Mutual Aid Agreements.........................................................................................10-52 Standardized Emergency Management System (SEMS) ..................................................................10-53 Santa Monica Office of Emergency Management ..........................................................................10-55 Santa Monica Police Department ..................................................................................................10-55 Southern California Edison (SCE) ...................................................................................................10-55 County Resources.............................................................................................................................10-56 Los Angeles County Fire Department ............................................................................................10-56 Los Angeles County Chief Executive Office ...................................................................................10-56 State Resources................................................................................................................................. 10-56 California Division of Forestry & Fire Protection and Office of the State Fire Marshal (OSFM) ......10-56 California Governor’s Office of Emergency Services (Cal-OES) .....................................................10-56 California FireSafe Council (CFSC) ................................................................................................10-56 Federal Resources and Programs ......................................................................................................10-56 Federal Emergency Management Agency (FEMA)..........................................................................10-57 U.S. Department of the Interior .....................................................................................................10-57 National Weather Service..............................................................................................................10-57 Other National Resources.................................................................................................................10-57 National Fire Protection Association (NFPA) .................................................................................10-57 National Interagency Fire Center (NIFC)........................................................................................10-57 United States Fire Administration (USFA) ......................................................................................10-58 Additional Resources........................................................................................................................10-58 Firewise USA................................................................................................................................. 10-58 Insurance Services Office (ISO) .....................................................................................................10-58 Publications......................................................................................................................................10-58

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City of Santa Monica, California
2025 Table of Contents – Volume II Page vii
TABLE OF CONTENTS (continued)
SECTION ......................................................................................... PAGE # Section 11: Climate Change and Severe Weather
WHY DO CLIMATE CHANGE AND SEVERE WEATHER POSE A THREAT TO THE CITY OF SANTA MONICA? ..................11-1 SNAPSHOT OF SANTA MONICA’S CLIMATE AND WEATHER BASED ON HISTORICAL DATA, AND ELEMENTS IMPACTING FUTURE FORECASTS.....................................................................................................................11-3 Extreme Heat......................................................................................................................................11-5 Social Vulnerability to Extreme Heat ...............................................................................................11-8 Extreme Heat Mitigation Actions and Resources............................................................................11-10 Drought ............................................................................................................................................11-13 Social Vulnerability to Drought .....................................................................................................11-14 Drought Planning and Mitigation Actions......................................................................................11-15 Sea-Level Rise...................................................................................................................................11-17 Sea-level Rise Projections in Santa Monica and Social Impacts.....................................................11-18 Sea-Level Rise Adaptation Strategies in Santa Monica ...................................................................11-22 Severe Windstorms...........................................................................................................................11-23 Social Vulnerability to Windstorms ...............................................................................................11-35 Activities for Windstorm Mitigation and Response ........................................................................11-36 Section 12: Hazardous Materials
WHY ARE HAZARDOUS MATERIALS A THREAT TO THE CITY OF SANTA MONICA? .................................................12-1 DEFINITIONS ...............................................................................................................................................12-2 What are Hazardous Materials?..........................................................................................................12-2 What is a Hazardous Material Release?..............................................................................................12-3 Conditions Conducive to Hazardous Material Releases......................................................................12-3 Releases from Leaking Underground Storage Tanks.........................................................................12-5 Spills Related to Transportation Accidents.......................................................................................12-5 Releases Due to Damaged Pipelines ...............................................................................................12-6 Releases Due to Earthquakes...........................................................................................................12-7 Inappropriate or Accidental Use of Hazardous Materials in Households.........................................12-7 HISTORICALLY AND LOCALLY SIGNIFICANT SOUTHERN CALIFORNIA RELEASES OF HAZARDOUS MATERIALS.............12-8 1987 Releases Related to the Whittier Narrows Earthquake................................................................12-8 1994 Releases Related to the Northridge Earthquake..........................................................................12-8 2019 405-Freeway Closure due to Overturned Truck .........................................................................12-9 2020 405-Freeway Closure due to Hazardous Spill............................................................................12-9 2020 Hazardous Material Spills..........................................................................................................12-9 2021 Hazardous Material Spills..........................................................................................................12-9 2022 Hazardous Material Spills........................................................................................................12-10 2023 Hazardous Material Spills........................................................................................................12-10 July 2024 Closure of I-15 due to Truck Fire ......................................................................................12-11 2024 Hazardous Material Spills........................................................................................................12-11 September 2024 Freeway Closure due to Truck Fire.........................................................................12-11 HAZARDOUS MATERIALS RELEASE ASSESSMENT FOR SANTA MONICA................................................................12-12 Hazard Identification........................................................................................................................12-12 Generators of Hazardous Materials ...............................................................................................12-12 Leaking Underground Storage Tanks (LUSTs) and Cleanup Program Sites.....................................12-17 Transporters of Hazardous Materials .............................................................................................12-19 Pipelines Through the City ............................................................................................................12-20 Vulnerability and Risk ......................................................................................................................12-20 HAZARDOUS MATERIALS MITIGATION ACTIVITIES ..........................................................................................12-23

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City of Santa Monica, California
2025 Table of Contents – Volume II Page viii
TABLE OF CONTENTS (continued)
SECTION ......................................................................................... PAGE # HAZARDOUS MATERIALS MANAGEMENT RESOURCE DIRECTORY......................................................................12-25 City Resources..................................................................................................................................12-25 Local Resources................................................................................................................................12-25 County Resources.............................................................................................................................12-26 State Resources................................................................................................................................. 12-26 Federal Resources.............................................................................................................................12-27 Section 13: Airport Hazards
WHAT AIRPORT ACTIVITIES COULD POSE A HAZARD TO THE CITY OF SANTA MONICA? .......................................13-1 BACKGROUND ............................................................................................................................................13-1 Airport Setting.....................................................................................................................................13-1 Santa Monica Airport History .............................................................................................................13-3 Airport Operations..............................................................................................................................13-6 HISTORICALLY AND LOCALLY SIGNIFICANT SOUTHERN CALIFORNIA AVIATION ACCIDENTS ...................................13-8 REGULATORY SETTING................................................................................................................................13-18 Airport Land Use Compatibility Planning Requirements...................................................................13-18 Airport Operations............................................................................................................................13-19 Aviation Noise..................................................................................................................................13-23 VULNERABILITY AND RISK ASSESSMENT .........................................................................................................13-27 Ground and Airspace Safety .............................................................................................................13-27 Aviation Noise..................................................................................................................................13-29 Potential for Hazardous Materials Related to Historical Airport Land Uses.......................................13-33 Social Vulnerability to Airport Hazards.............................................................................................13-35 AIRPORT HAZARDS MITIGATION ACTIVITIES ..................................................................................................13-37 AIRPORT HAZARDS RESOURCE DIRECTORY ...................................................................................................13-38 City Resources..................................................................................................................................13-38 County Resources............................................................................................................................. 13-39 State Resources................................................................................................................................. 13-39 Federal Resources and Programs ......................................................................................................13-40 Publications......................................................................................................................................13-40 VOLUME III – APPENDICES
Appendix A: Master Resource Directory....................................................................... A-1 Appendix B: Public Participation Process and Meeting Materials.................................. B-1 Appendix C: Economic Analysis of Natural Hazard Mitigation Projects........................ C-1 Appendix D: Acronyms............................................................................................... D-1 Appendix E: Glossary .................................................................................................. E-1 Appendix F: California Disasters Since 1950................................................................ F-1 Appendix G: Major Dams in Los Angeles County ........................................................ G-1 Appendix H: Plates ...................................................................................................... H-1 Appendix I: References ................................................................................................ I-1 Appendix J: City Council Adoption Resolution............................................................. J-1

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TABLE OF CONTENTS (continued)
SECTION ......................................................................................... PAGE #

TABLES, FIGURES AND PHOTOS
Tables
Table 6-1: Abridged Modified Mercalli Intensity Scale ............................................................................. 6-6 Table 6-2: Historical (1769 – March 2024) Earthquakes in the Southern California Region with Magnitudes > 4.5........................................................................................................... 6-11 Table 6-3: Estimated Horizontal Peak Ground Accelerations and Seismic Intensities in the Santa Monica Area ................................................................................................................ 6-21 Table 6-4: Injury Classification Scale...................................................................................................... 6-58 Table 6-5: HazUS Earthquake Scenarios for the City of Santa Monica.................................................... 6-61 Table 6-6: Building Exposure by Occupancy Type for the Study Area .................................................... 6-62 Table 6-7: Number of Buildings Damaged, by Construction Type.......................................................... 6-62 Table 6-8: Number of Buildings Damaged, by Occupancy Type............................................................ 6-64 Table 6-9: Building-Related Economic Loss Estimates (in Million $) ....................................................... 6-70 Table 6-10: Estimated Transportation and Utility System Economic Losses............................................... 6-71 Table 6-11: Estimated Casualties .............................................................................................................. 6-73 Table 6-12: Estimated Damage to Critical Facilities as a Result of the Earthquake Scenarios .................... 6-74 Table 6-13: Estimated Damage to Pipelines as a Result of Three Earthquake Scenarios............................ 6-76 Table 6-14: Expected Performance of Potable Water and Electricity Services........................................... 6-77 Table 6-15: Fires Following an Earthquake ............................................................................................... 6-78 Table 6-16: Debris Generated by Earthquake Scenarios ........................................................................... 6-79 Table 6-17: Partial List of Over 200 California Laws on Earthquake Safety ............................................... 6-79 Table 7-1: Significant Historical Tsunami Record for Southern California – 1812 to January 2024........... 7-6 Table 7-2: Total Building and Total Residential Building Damage Counts for Los Angeles County Based on a HazUS Tsunami Analysis of the CGS (2021) Tsunami Hazard Maps for California ........ 7-21 Table 7-3: Estimated Tsunami Casualties in Santa Monica by Time of Day, Exposed Population and Community Preparedness Level (for a Local Tsunami Scenario) ............................................ 7-22 Table 7-4: Estimated Economic Losses to Residential and Commercial Buildings in Santa Monica Using Crisis Track® Software ................................................................................................ 7-23 Table 7-5: Tsunami Alerts and Appropriate Responses ........................................................................... 7-24 Table 8-1: Historical Floods in Los Angeles County.................................................................................. 8-5 Table 8-2: Tropical Storms That Affected Southern California Between 1858 and August 2023 ............. 8-10 Table 8-3: Flood Zones Mapped in Santa Monica .................................................................................. 8-21 Table 8-4: Dam Failures in Southern California...................................................................................... 8-26 Table 8-5: Water Storage Reservoirs In and Near Santa Monica Owned by Santa Monica ..................... 8-32 Table 8-6: Building Exposure by Occupancy Type – Stone Canyon Dam Inundation Event ................... 8-40 Table 8-7: Estimated Economic Losses to Residential and Commercial Buildings in Santa Monica Within the 100-Year Flood Zone Using Crisis Track® Software ........................................................ 8-41 Table 8-8: Expected Building Damage by Occupancy as a Result of a Stone Canyon Dam Failure ........ 8-42 Table 8-9: Expected Building Damage by Building Type ........................................................................ 8-42 Table 8-10: Building-Related Economic Loss Estimates Resulting from a Catastrophic Stone Canyon Dam Failure Scenario ............................................................................................................ 8-44 Table 8-11: Estimated Economic Losses to Residential and Commercial Buildings in Santa Monica Within the Stone Canyon Dam Inundation Zone Using Crisis Track® Software..................... 8-44 Table 10-1: Top Twenty Most-Destructive Fires in California (as of April 3, 2025) Based on Total Number of Structures Destroyed............................................................................................10-6 Table 10-2: Zones in Santa Monica Under Evacuation Orders and Evacuation Warnings During the Palisades Fires of January 2025............................................................................................10-16

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TABLE OF CONTENTS (continued)
SECTION ......................................................................................... PAGE # Table 10-3: Causes of Residential Building Fires in the U.S. (2017-2019), Organized from Highest to Lowest Percentages .............................................................................................................10-29 Table 10-4: Fires Following an Earthquake .............................................................................................10-38 Table 10-5: Santa Monica Fire Department Stations, Resources and Minimum Daily Staffing ................10-52 Table 11-1: Summary of Natural Hazard Events in California (1980-Sept. 2024) Costing >$1 Billion.......11-2 Table 11-2: Record Monthly Temperatures (°F) and Years of Record in Santa Monica .............................11-6 Table 11-3: Santa Monica Projected Heat Health Events..........................................................................11-9 Table 11-4: Projected Sea-Level Rise Scenarios for Santa Monica ..........................................................11-19 Table 11-5: Anticipated Costs of Sea Level Rise in Santa Monica (in millions of $) Through the Year 2100........................................................................................................11-22 Table 11-6: Selected Extreme Wind Events Reported in the Santa Monica Region Through June 2024.

Santa Ana Wind events are highlighted in yellow................................................................11-24 Table 11-7: Enhanced Fujita Scale..........................................................................................................11-31 Table 11-8: Tornado Events in the Santa Monica Region........................................................................11-32 Table 12-1: TRI Site, and Large-Quantity Generators (LQGs) of Hazardous Materials in the City of Santa Monica.......................................................................................................................12-14 Table 12-2: Open Leaking Underground Fuel Tank (LUST) and Cleanup Program Sites in the City of Santa Monica.......................................................................................................................12-18 Table 12-3: Routes in the Vicinity of Santa Monica Used to Transport Hazardous Materials and Explosives.....................................................................................................................12-20 Table 13-1: Annual Flight Operations at SMO, 2018-2023 ......................................................................13-7 Table 13-2: Significant Historical Aviation Accidents and Incidents in Southern California......................13-9 Table 13-3: Aircraft Incidents Reported for SMO between 1964 and 2024.............................................13-14 Table 13-4: Noise Complaints Related to SMO Operations, 2018-2023.................................................13-33 Figures
Figure 6-1: Regional Map Showing Select Faults, Physiographic Provinces and Landforms Mentioned in the Text .............................................................................................................................. 6-2 Figure 6-2: Main Types of Faults................................................................................................................ 6-4 Figure 6-3: Earthquake Shaking Levels Anticipated in California ............................................................... 6-8 Figure 6-4: Notable Regional Earthquakes............................................................................................... 6-12 Figure 6-5: ShakeMap for a Magnitude 7.4 Earthquake Scenario on the Malibu Coast-Santa MonicaHollywood Fault System........................................................................................................ 6-24 Figure 6-6: ShakeMap for a Magnitude 7.2 Earthquake Scenario on the Newport-Inglewood Fault......... 6-27 Figure 6-7: ShakeMap for a Magnitude 7.5 Earthquake Scenario on the Compton Thrust Fault ............... 6-29 Figure 6-8: Scenario for a M7.1 Earthquake Scenario on the Puente Hills Fault Showing Estimated Intensity Values in the Region Resulting from this Event ...................................................................... 6-30 Figure 6-9: Estimated Percent Building Loss as a Result of a Mw 7.5 Earthquake on the Puente Hills Thrust ................................................................................................................ 6-31 Figure 6-10: ShakeMap for a Magnitude 7.8 Earthquake Scenario on the San Andreas Fault (repeat of the 1857 Fort Tejon Earthquake) ............................................................................ 6-35 Figure 6-11: ShakeMap for a Magnitude 7.8 Earthquake Scenario (Shakeout) on the San Andreas Fault.... 6-36 Figure 6-12: Faults Mapped and Inferred Through, Near and Below Santa Monica ................................... 6-40 Figure 6-13: Earthquake Fault Zones of Required Investigation In and Near Santa Monica, California ...... 6-43 Figure 6-14: Seismic Hazards Zones Map, Santa Monica, California......................................................... 6-45 Figure 6-15: Census Tracts Used in the HazUS Analyses........................................................................... 6-60

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TABLE OF CONTENTS (continued)
SECTION ......................................................................................... PAGE # Figure 6-16: Total Residential Building Related Losses as a Percentage of Total Residential Building Exposure.................................................................................................................. 6-67 Figure 6-17: Total Commercial Building Related Losses as a Percentage of Total Commercial Building Exposure.................................................................................................................. 6-68 Figure 7-1: Bathymetric Map of Santa Monica Bay Showing Continental Slope and Offshore Canyons that Could be a Source of Tsunami-Generated Landslides....................................................... 7-1 Figure 7-2: Diagram Showing Terms Commonly Used in Tsunami Studies................................................ 7-2 Figure 7-3: World Map Showing Approximate Location of Ring of Fire (pink shaded areas), Subduction Trenches (blue lines), Active Volcanoes (yellow triangles), and Large Earthquakes Between 1900 and 2013 (red, green and blue dots). Cascadia Subduction Zone also shown................. 7-4 Figure 7-4: Tsunami Hazards Map, Santa Monica, California .................................................................. 7-18 Figure 8-1: Annual Rainfall in the City of Los Angeles, California for the Period Between 1877 and 2023................................................................................................................................. 8-2 Figure 8-2: Tile Plot Showing Monthly Discharges in Ballona Creek at Site 11103500 for Years 1928-1978 ..................................................................................................................... 8-4 Figure 8-3: Flood Zones Mapped In and Near Santa Monica................................................................... 8-23 Figure 8-4: Dam Inundation Map ............................................................................................................ 8-37 Figure 8-5: Anticipated Damage in Santa Monica as a Result of a Stone Canyon Dam Failure Scenario . 8-43 Figure 9-1: Physiographic Map of Santa Monica and Surrounding Areas................................................... 9-2 Figure 9-2: Geologic Map of Santa Monica and Vicinity with Unit Descriptions....................................... 9-3 Figure 9-3: Bathymetric Map of Santa Monica Bay Showing Offshore Canyons ........................................ 9-5 Figure 9-4: Slope Distribution Map for Santa Monica and Adjoining Areas ............................................. 9-14 Figure 9-5: Areas in Santa Monica Susceptible to Slope Failure............................................................... 9-16 Figure 10-1: Wildfires Causes for the Period 2010-2020 in California (top) and in Los Angeles County (bottom)................................................................................................................................. 10-3 Figure 10-2: Historical (1930-2025) Wildfires Near Santa Monica ............................................................10-5 Figure 10-3: Federal Responsibility Areas (FRAs) in light green and State Responsibility Areas (SRAs) in yellow to the north and northwest of Santa Monica as of December 31, 2024 ....................10-24 Figure 10-4: Fire Hazard Severity Zones In and Near Santa Monica, California.......................................10-26 Figure 10-5: Various Statistics for Fire Losses in the United States, 1980-2023........................................10-28 Figure 10-6: Wildfire Risk Profile for Santa Monica, California................................................................10-39 Figure 11-1: Impacts of Climate Change on California ..............................................................................11-1 Figure 11-2: Health Impacts of Climate Change ........................................................................................11-2 Figure 11-3: Projections of Maximum Temperatures and Extreme Heat Days in Santa Monica (1950-2100) under RCP 4.5 (teal) and 8.5 (violet)..................................................................11-7 Figure 11-4: 2022 California Drought, Five-Category System ..................................................................11-13 Figure 11-5: Percent of Los Angeles County in U.S. Drought Monitor Categories: 2000-2024.................11-14 Figure 11-6: Projected Sea-Level Rise Scenarios for Santa Monica ..........................................................11-19 Figure 11-7: Flood Extent along the Santa Monica Coastline Through the Year 2100 Using Three Sea-Level Rise Scenarios......................................................................................................11-21 Figure 11-8: Santa Ana Winds.................................................................................................................11-24 Figure 11-9: Funnel Cloud Over the Ocean off Venice Beach, Feb. 22, 2005 .........................................11-31 Figure 12-1: Map of the impacted area where a multi-day power outage was required to complete repairs to the gas main break. Actual damage occurred on Lipton Avenue at Stanford Street ..............12-10 Figure 12-2: Hazardous Materials Sites, Santa Monica, California...........................................................12-16 Figure 13-1: Regional Setting of the Santa Monica Airport.........................................................................13-2 Figure 13-2: Land Use Around Santa Monica Airport ................................................................................13-5 Figure 13-3: Annual Operations by Year at SMO, 2001-2023 ...................................................................13-7

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Figure 13-4: The Four Safety Management System (SMS) Components....................................................13-20 Figure 13-5: Airport Influence Zones.......................................................................................................13-22 Figure 13-6: Typical Noise Levels............................................................................................................13-24 Figure 13-7: Single Event Noise Exposure Level (SENEL) .........................................................................13-26 Figure 13-8: Noise Contours for SMO .....................................................................................................13-32 Figure 13-9: Social Vulnerability of Census Tracts Near the Santa Monica Airport (showing nursing homes, schools, and child care centers)..................................................................13-36 Photos
Photo 8-1: Failure of the Baldwin Hills Dam ....................................................................................... 8-28 Photo 12-1: View to the northwest along Stanford Street, from just south of Lipton Avenue, of the street closures and potholing required to fix the gas main .........................................................12-10 Photo 12-2: View of damaged gas main under repair ..........................................................................12-10

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SECTION 6: EARTHQUAKES
WHY ARE EARTHQUAKES A THREAT TO THE CITY OF SANTA MONICA? Santa Monica is at risk from many natural and man-made hazards, and an earthquake is an event that poses a great potential for far-reaching loss of life or property, and economic damage. This is true for most of southern California, since damaging earthquakes occur relatively frequently, affect widespread areas, trigger many secondary effects, and can overwhelm the ability of local jurisdictions to respond. Earthquake-triggered geologic effects include ground shaking, surface fault rupture, landslides, liquefaction, subsidence, seiches and if offshore, tsunamis (see Section 7).

Earthquakes can also cause human-made hazards such as dam failures (see Section 8), urban fires (Section 11), and toxic chemical releases (see Section 12).

In California, recent earthquakes in or near urban environments have caused relatively few casualties. This is due more to luck than design. For example, when a portion of the Nimitz Freeway in Oakland collapsed at rush hour during the 1989, MW 7.1 Loma Prieta earthquake, the freeway was uncommonly empty because so many were watching the World Series. The 1994, MW 6.7 Northridge earthquake occurred before dawn, when most people were home safely in bed.

Despite such good luck, California’s urban earthquakes have resulted in significant losses. The moderate-sized Northridge earthquake caused 54 deaths, more than 1,500 injuries and nearly $30 billion in damage. For days afterward, thousands of homes and businesses were without electricity; tens of thousands had no gas; and nearly 50,000 had little or no water. Approximately 15,000 structures were moderately to severely damaged, which left thousands of people temporarily homeless. Santa Monica experienced a relatively large number of damaged buildings, including to its hospitals. Several collapsed bridges and overpasses created commuter and commercial transport havoc on the freeway system. Extensive damage was caused by ground shaking, with shaking-induced liquefaction and dozens of fires after the earthquake causing additional damage. This moderately sized earthquake resulted in record economic losses, and yet the Los Angeles metropolitan area, including the city of Santa Monica, is at risk from earthquakes that could release more than ten times the seismic energy of the Northridge earthquake.

Historical and geological records show that California has a long history of seismic events. The state is probably best known for the San Andreas fault, an approximately 750-mile-long fault zone running from the Mexican border to a point offshore west of San Francisco. Geologic studies show that over the past 1,400 to 1,500 years, large earthquakes have occurred on the southern San Andreas fault at about 130-year intervals. As the last large earthquake on the southern San Andreas occurred in 1857, that section of the fault is considered a likely location for an earthquake within the next few decades. The San Andreas fault, however, is only one of dozens of known faults that extend across southern California. Some of the better-known faults include the Sierra Madre, Newport-Inglewood, Whittier-Elsinore, Santa Monica, Hollywood, Malibu Coast and Palos Verdes faults (see Figure 6-1). The Santa Monica fault extends through the northern portion of the city. The Malibu Coast, Palos Verdes, Hollywood, Newport-Inglewood and Compton faults are located within about 10 miles of Santa Monica, and thus have the capacity to generate strong shaking in the city, stronger than what an earthquake on the San Andreas fault would produce. Each of these faults is discussed in detail later in this section.

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Great advances in earthquake engineering have been made in the last three decades in large part as a result of the lessons learned from the 1994 Northridge, California, 1995 Kobe, Japan, 1999 Izmit, Turkey and 1999 Chi-Chi, Taiwan earthquakes. The 1994 Northridge earthquake in particular engendered several changes first adopted in 1997 to the building code used in California. Nevertheless, many California communities remain unprepared, partly because the

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building code changes are not retroactive and thus many older structures have not been strengthened. In the past decade, however, this has changed in some areas, with several cities, including Santa Monica, requiring seismic retrofits of several construction styles that are known to perform poorly in earthquakes. Thus, with the application of the latest building codes and the enforcement of seismic retrofits for older structures, it is possible to minimize the destructive effects of earthquakes.

Comprehensive hazard mitigation programs that include the identification and mapping of hazards, prudent planning, public education, emergency exercises, enforcement of building codes, and expedient retrofitting and rehabilitation of weak structures can significantly reduce the scope of an earthquake’s effects and avoid disaster. The objective is for local governments, emergency relief organizations, and residents to take action and develop and implement policies and programs designed to reduce the effects of earthquakes. Undoubtedly these improvements will be tested the next time the region experiences a moderate- to large-magnitude earthquake.

EARTHQUAKE BASICS - DEFINITIONS
The outer 10 to 70 kilometers of the Earth consist of enormous blocks of moving rock, called plates. There are about a dozen major plates, which slowly collide, separate, and grind past each other. In the uppermost plates, friction locks the plate edges together, while movement continues at depth. Consequently, the near-surface rocks bend and deform near plate boundaries, storing strain energy. Eventually, the frictional forces are overcome and the locked portions of the plates move. The stored strain energy is released in waves.

By definition, the break or fracture between moving blocks of rock is called a fault, and such differential movement produces a fault rupture. The place where the fault first ruptures is called the focus (or hypocenter). The released energy waves radiate out in all directions from the rupture surface, making the earth vibrate and shake as the waves travel through. This shaking is what we feel in an earthquake.

Although earthquakes can occur in areas with no known faults, most earthquakes occur on or near plate boundaries. Given that California straddles the boundary between the North American and Pacific plates (Figure 6-1), it experiences many earthquakes, and relatively often. The Pacific Plate is moving northwesterly, relative to the North American Plate, at about 52 mm/yr (2 inches/yr).

This is about the rate at which fingernails grow, and seems unimpressive. However, it is enough to accumulate enormous amounts of strain energy over dozens to thousands of years. Despite being locked in place most of the time, in another 15 million years (a short time in the context of the Earth’s history), due to plate movements, Santa Monica will be hundreds of kilometers north of San Francisco.

Although the San Andreas fault marks the actual separation between the Pacific and North American plates, only about 70 percent of the plate motion occurs on the San Andreas fault itself.

The rest is distributed among other faults of the San Andreas system, including the San Jacinto, Whittier-Elsinore, Newport-Inglewood, Palos Verdes, plus several offshore faults; and among faults of the Eastern Mojave Shear Zone, a series of faults east of the San Andreas fault that were responsible for the 1992 Landers, 1999 Hector Mine and 2019 Ridgecrest earthquakes. Thus, the zone of plate-boundary earthquakes and ground deformation covers an area that stretches from the Pacific Ocean to Nevada.

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Because the Pacific and North American plates are sliding past each other, with relative motions to the northwest and southeast, respectively, all of the faults mentioned above are aligned northwestsoutheast, and are strike-slip faults (see Figure 6-1). On average, strike-slip faults are nearly vertical breaks in the rock, and when a strike-slip fault ruptures, the rocks on either side of the fault slide horizontally past each other.

However, about 70 miles northwest of Santa Monica, there is a kink in the San Andreas fault, commonly referred to as the “Big Bend.” Near the Big Bend, the two plates do not slide past each other. Instead, they collide, causing localized compression, resulting in folding and thrust faulting (see Figure 6-2). Thrust faults meet the surface of the Earth at a low angle, dipping 25 to 45 degrees from the horizontal. Thrusts are a type of dip-slip fault, where rocks on opposite sides of the fault move up or down relative to each other. When a thrust fault ruptures, the top block of rock moves up and over the rock on the other side of the fault.

Figure 6-2: Main Types of Faults
Few faults are simple, planar breaks in the Earth. They more often consist of smaller strands, with a similar orientation and sense of movement. Sometimes geologists group strands into sections or segments, which are believed capable of rupturing together during a single earthquake. The more extensive the fault, the bigger the earthquake it can produce. Therefore, multi-strand fault ruptures generally produce larger earthquakes.

Large-magnitude earthquakes that occur near urban centers have the potential to cause the most damage. Thus, fault dimensions and proximity to urban centers are key parameters in any hazard assessment. In addition, it is important to know a fault’s style of movement (i.e., is it dip-slip or strike-slip), the age of its most recent activity, its total displacement, and its slip rate (all discussed below). These values are helpful in estimating how often a fault produces damaging earthquakes, Strike-slip faults are vertical or almost vertical
rifts where the earth’s plates move mostly
horizontally. From the observer’s perspective, if
the opposite block, looking across the fault,
moves to the right, the fault is a right-lateral
fault; if the block moves left, the fault is a leftlateral fault.

Dip-slip faults are slanted structures where the blocks mostly shift vertically. If the rock above an inclined fault moves down, the fault is called a normal fault; when the rock above the fault moves up, the fault is called a reverse fault. Thrust faults are reverse faults with a dip of 45° or less.

Normal fault Reverse fault
Strike-slip fault

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and the size of the earthquake that will be generated the next time that fault ruptures. Most large damaging earthquakes are followed by aftershocks. By definition, these are smaller earthquakes that happen close to the mainshock (the biggest earthquake of the sequence) in time and space.

These smaller earthquakes occur as the Earth adjusts to the regional stress changes created by the mainshock. The bigger the mainshock, the greater the number of aftershocks, the larger the aftershocks will be, and the wider the area in which they might occur. On average, the largest aftershock will be 1.2 magnitude units less than the mainshock. This is an average, and there are many cases where the biggest aftershock is larger than the average predicts. The key point is that any major earthquake will produce aftershocks large enough to cause additional damage, especially to already weakened structures. Consequently, post-disaster response planning must take damaging aftershocks into account.

When comparing the sizes of earthquakes, the most meaningful feature is the amount of energy released. Thus, scientists most often consider seismic moment, a measure of the energy released when a fault ruptures. We are more familiar, however, with scales of magnitude, which measure amplitude of ground motion. Magnitude scales are logarithmic. Each one-point increase in magnitude represents a ten-fold increase in amplitude of the waves as measured at a specific location, and a 32-fold increase in energy. That is, a magnitude 7 earthquake produces 100 times (10 x 10) the ground motion amplitude of a magnitude 5 earthquake. Similarly, a magnitude 7 earthquake releases approximately 1,000 times more energy (32 x 32) than a magnitude 5 earthquake. Scientists now use the moment magnitude (Mw) scale to relate energy release to magnitude; this scale has replaced the Richter scale, which is no longer used by seismologists.

An early measure of earthquake size still used today is the seismic intensity scale, which is a qualitative assessment of an earthquake’s effects at a given location. Although it has limited scientific application, intensity is still widely used because it is intuitively clear and quick to determine. The most commonly used measure of seismic intensity is called the Modified Mercalli Intensity (MMI) scale, which has 12 levels of damage (see Table 6-1).

A given earthquake will have one seismic moment and, in principle, one magnitude, although there are several methods of calculating magnitude, which give slightly different results. However, one earthquake will produce several intensities because intensity effects vary with the location (distance), soil conditions, and perceptions of the observer.

Total displacement is the length, measured in kilometers (km), of the total movement that has occurred along the fault over as long a time as the geologic record reveals. It is usually estimated by measuring the distance between geologic features (such as a distinctive rock formation) that have been split apart and separated (offset) by the cumulative movement of the fault over many earthquakes. Slip rate is a speed, expressed in millimeters per year (mm/yr). Slip rate is estimated by measuring an amount of offset accrued during a known amount of time, obtained by dating the ages of geologic features. Slip rate data also are used to estimate a fault’s earthquake recurrence interval. Sometimes referred to as “repeat time” or “return interval,” the recurrence interval represents the average amount of time that elapses between major earthquakes on a fault.

Geologists generally derive the recurrence interval for a fault by excavating a series of trenches across the fault to obtain paleoseismic evidence of the earthquakes that have occurred during prehistoric time. If the sediments exposed in the trenches are suitable for dating and the earthquake record is well preserved, geologists can date (typically with a certain margin of error) the past earthquakes, and from that data, develop an average earthquake recurrence interval for that fault segment.

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Table 6-1: Abridged Modified Mercalli Intensity Scale
2BIntensity Value and Description
Average Peak
Velocity
(cm/sec)
Average Peak
Acceleration
(g = gravity)
I. Not felt except by a very few under especially favorable circumstances (I Rossi-Forel scale). Damage potential: None. <0.1 <0.0017 II. Felt only by a few persons at rest, especially on upper floors of high-rise buildings. Delicately suspended objects may swing. (I to II Rossi-Forel scale).

Damage potential: None.

III. Felt quite noticeably indoors, especially on upper floors of buildings, but 0.1 – 1.1 0.0017 – 0.014 many people do not recognize it as an earthquake. Standing automobiles may rock slightly. Vibration like passing of truck. Duration estimated. (III Rossi-Forel scale). Damage potential: None.

IV. During the day felt indoors by many, outdoors by few. At night some awakened. Dishes, windows, doors disturbed; walls make creaking sound.

Sensation like a heavy truck striking building. Standing automobiles rocked noticeably. (IV to V Rossi-Forel scale). Damage potential: None. Perceived shaking: Light.

1.1 – 3.4 0.014 - 0.039
V. Felt by nearly everyone; many awakened. Some dishes, windows, and so on broken; cracked plaster in a few places; unstable objects overturned.

Disturbances of trees, poles, and other tall objects sometimes noticed.

Pendulum clocks may stop. (V to VI Rossi-Forel scale). Damage potential:

Very light. Perceived shaking: Moderate.

3.4 – 8.1 0.039-0.092
VI. Felt by all; many frightened and run outdoors. Some heavy furniture moved, few instances of fallen plaster and damaged chimneys. Damage slight. (VI to VII Rossi-Forel scale). Damage potential: Light. Perceived shaking: Strong.

8.1 - 16 0.092 -0.18
VII. Everybody runs outdoors. Damage negligible in buildings of good design and construction; slight to moderate in well-built ordinary structures; considerable in poorly built or badly designed structures; some chimneys broken. Noticed by persons driving cars. (VIII Rossi-Forel scale). Damage potential: Moderate.

Perceived shaking: Very strong.
16 - 31 0.18 - 0.34
VIII. Damage slight in specially designed structures; considerable in ordinary substantial buildings with partial collapse; great in poorly built structures.

Panel walls thrown out of frame structures. Fall of chimneys, factory stacks, columns, monuments, and walls. Heavy furniture overturned. Sand and mud ejected in small amounts. Changes in well water. Persons driving cars disturbed. (VIII+ to IX Rossi-Forel scale). Damage potential: Moderate to heavy. Perceived shaking: Severe.
31 - 60 0.34 - 0.65
IX. Damage considerable in specially designed structures; well-designed frame structures thrown out of plumb; great in substantial buildings with partial collapse. Buildings shifted off foundations. Ground cracked conspicuously.

Underground pipes broken. (IX+ Rossi-Forel scale). Damage potential:

Heavy. Perceived shaking: Violent.
60 - 116 0.65 – 1.24
X. Some well-built wooden structures destroyed; most masonry and frame structures destroyed; ground badly cracked. Rails bent. Landslides considerable from river banks and steep slopes. Shifted sand and mud. Water splashed, slopped over banks. (X Rossi-Forel scale). Damage potential: Very heavy. Perceived shaking: Extreme.
> 116 > 1.24
XI. Few, if any, (masonry) structures remain standing. Bridges destroyed. Broad fissures in ground. Underground pipelines completely out of service. Earth slumps and land slips in soft ground. Rails bent greatly.

XII. Damage total. Waves seen on ground surface. Lines of sight and level distorted. Objects thrown into air.

Modified from Bolt (1999); Wald et al. (1999).

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In southern California, ruptures along thrust faults have built the Transverse Ranges geologic province, a region with an east-west trend to its landforms and underlying geologic structures (Figure 6-1). This orientation is anomalous, virtually unique in the western United States, and a direct consequence of the plates colliding at the Big Bend. Many of southern California’s most recent damaging earthquakes have occurred on thrust faults that are uplifting the Transverse Ranges, including the 1971 San Fernando, the 1987 Whittier Narrows, the 1991 Sierra Madre, and the 1994 Northridge earthquakes. In addition to generating stronger ground shaking than a similarmagnitude earthquake on a strike-slip fault, thrust faults are also particularly hazardous because many are blind, that is, they do not extend to the surface of the Earth. These blind thrust faults are extremely difficult to detect before they rupture. Both the 1987 Whittier Narrows and the 1994 Northridge earthquakes occurred on blind thrust faults.

CAUSES OF EARTHQUAKE DAMAGE
Causes of earthquake damage can be categorized into three general areas: strong shaking, various types of ground failure that are a result of shaking, and ground displacement along the rupturing fault.

Ground shaking is the motion felt on the earth's surface caused by seismic waves generated by the earthquake. It is the primary cause of earthquake damage, and is typically reported as the peak horizontal ground acceleration estimated as a percentage of g, the acceleration of gravity. Full characterization of shaking potential, though, requires estimates of peak (maximum) ground displacement and velocity, the duration of strong shaking, and the periods (lengths) of waves that will control each of these factors at a given location. The strength of ground shaking also depends on the source, path, and site effects. Estimates of the ground shaking that different locations in California are likely to experience have been mapped, as shown on Figure 6-3. This figure shows that only the easternmost portion of southern California and a portion of San Diego County may be beyond the reach of a damaging earthquake (green areas). • Source effects include earthquake size, location, and distance, plus directivity of the seismic waves (for example, the 1995, MW 6.9, Kobe, Japan earthquake was not much bigger than the 1994, MW 6.7 Northridge, California earthquake, but Kobe caused much worse damage. During the Kobe earthquake, the fault’s orientation and movement directed seismic waves into the city, whereas during the Northridge earthquake, the fault’s motion directed waves away from populous areas.
• Path effects refer to how the seismic waves change direction as they travel through the Earth’s contrasting layers, just as light bounces (reflects) and bends (refracts) as it moves from air to water. Sometimes seismic energy gets focused into one location and causes damage in unexpected areas (focusing of the seismic waves generated by the 1989 MW 7.1 Loma Prieta earthquake caused damage in San Francisco’s Marina district, some 100 km distant from the rupturing fault).
• Site effects refer to how seismic waves interact with the ground surface. Seismic waves slow down in the loose sediments and weathered rock at the Earth’s surface; as they slow, their energy converts from speed to amplitude, which heightens shaking (amplification).

Therefore, buildings on poorly consolidated and thick soils will typically see more damage than buildings on consolidated soils and bedrock. Amplification can also occur in areas on

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deep, sediment-filled basins and on ridge tops. Seismic waves can also get trapped at the surface and reverberate (resonate). Whether resonance will occur depends on the period (the length) of the incoming waves – long-period seismic waves, which are created by large earthquakes, are most likely to reverberate and cause damage in structures like bridges and high-rises, known as “long-period structures” for their response to these waves.

Shorter-period seismic waves, which tend to die out quickly, will most often cause damage fairly near the fault, and they will cause most damage in “shorter-period structures,” such as one- to three-story buildings. Very short-period waves are most likely to cause nearfault, interior damage, such as to equipment.

Figure 6-3: Earthquake Shaking Levels Anticipated in California Map shows the level of ground shaking with a 2 percent chance of exceedance in 50 years anticipated to occur throughout the state. The pink and red zones can experience higher ground shaking because they are closer to active faults.

The white star shows the approximate location of Santa Monica.

Source: Modified from Branum, D., Chen, R., Petersen, M., and Wills, C., 2016, Earthquake Shaking Potential for California: California Geological Survey Map Sheet 48; available in its entirety from https://www.conservation.ca.gov/cgs/documents/publications/map-sheets/MS_048.pdf.

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Earthquake damage also depends on the characteristics of human-made structures, with the interaction of ground motion with the built environment being complex. Governing factors include a structure’s height, construction, and stiffness, architectural design, condition, and age.

Liquefaction typically occurs within the upper 50 feet of the surface, where saturated, loose, fineto medium-grained soils (sand and silt) are present. Earthquake shaking suddenly increases pressure in the water that fills the pores between soil grains, causing the soil to lose strength and behave as a liquid. This process can be observed at the beach by standing on the wet sand near the surf zone. Standing still, the sand will support your weight. However, when you tap the sand with your feet, water comes to the surface, the sand liquefies, and your feet sink.

Liquefaction-related effects include loss of bearing strength, ground oscillations, lateral spreading and flow failures or slumping. The excess water pressure is relieved by the ejection of material upward through fissures and cracks. When soils liquefy, the structures built on them can sink, tilt, and suffer significant structural damage. Buildings and their occupants are at risk when the ground can no longer support the buildings.

Earthquake-induced landslides and rockfalls are secondary earthquake hazards that occur from ground shaking. Gravity inexorably pulls hillsides down, and earthquake shaking enhances this on-going process. Landslides and rockfalls can destroy roads, buildings, utilities, and other critical facilities necessary to respond and recover from an earthquake. Many communities in southern California with steep slopes have a high likelihood of being impacted by earthquake-induced landslides or rockfalls. Earthquake-induced slope failures are discussed in this section whereas landslide hazards are discussed in Section 9.

Primary ground rupture due to fault movement typically results in a relatively small percentage of the total damage in an earthquake, yet being too close to a rupturing fault can result in extensive damage. It is difficult, although not impossible, to safely reduce the effects of this hazard through building and foundation design. Therefore, the primary mitigation measure is to avoid active faults by setting structures back from the fault zone. Application of this measure is subject to the requirements of the Alquist-Priolo Earthquake Fault Zoning Act and guidelines established by the California Geological Survey. The Santa Monica fault has been mapped through the northern portion of Santa Monica, so this hazard is discussed further in this section.

HISTORY OF EARTHQUAKE EVENTS IN SOUTHERN CALIFORNIA
To better understand earthquake hazards, scientists study past earthquakes by looking at their records, and by studying the effects that past earthquakes had on the ground surface and the built environment. Historical earthquake records are either from the instrumental period (since about 1932, when the first seismographs were deployed), or pre-instrumental. In the absence of instrumentation, the detection and record of earthquakes are based on observations and felt reports, and are dependent upon population density and distribution.

Since California was sparsely populated in the 1800s, our record of pre-instrumental earthquakes is relatively incomplete. However, two very large earthquakes, the Fort Tejon in 1857 (M7.9) and the Owens Valley in 1872 (M7.6), are evidence of the tremendously damaging potential of earthquakes in southern California. More recently, two M7.3 earthquakes struck southern California, in Kern County (1952) and Landers (1992), and two M7.1 earthquakes struck the

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Mojave Desert (Hector Mine, in 1999 and Ridgecrest in 2019). The damage from all of these large earthquakes was limited because they occurred in sparsely populated areas. A similarly sized earthquake closer to southern California’s population centers has the potential to place millions of people at risk.

Since seismologists started recording and measuring earthquakes, there have been millions (if not billions) of recorded earthquakes in southern California. In fact, Ross et al. (2019) described a new earthquake detection technique that they applied to the 2008-2017 waveform archive for southern California and recognized approximately 1.81 million earthquakes during that ten-year time frame, amounting to ten times the number of earthquakes in the Southern California Seismic Network (SCSN) catalog that had been previously recognized for the same time period. That averages to about 495 earthquakes per day in the area, with an interval between earthquakes of 174 seconds.

The vast majority of these earthquakes are very small, of magnitude less than 1.0.

Table 6-2 lists the moderate to large historical earthquake events that have affected southern California, generally of magnitudes greater than about 4.5. Figure 6-4 shows the most significant historical earthquakes in the southern California region. Those earthquakes known or inferred to have been felt strongly in the Santa Monica area, or that led to the passage of important legislation, are discussed further in the sub sections below. For the known or inferred epicentral location of most of these earthquakes, refer to Figure 6-4.

Unnamed Earthquake of 1769
On July 28, 1769, the first recorded earthquake in southern California was noted by Spanish explorers traveling north with Gaspar de Portolá. At the time of the earthquake, the explorers were camped at the location of the present-day community of Olive, in the city of Orange, on the east bank of the Santa Ana River. Father Juan Crespo, who kept a daily account of the expedition, reported a strong mainshock followed by five days of moderate aftershocks. An estimated magnitude of at least 6.0 has been assigned to the main earthquake based on the explorers’ account (Teggart, 1911). The source for this earthquake is unknown, and still being debated by the paleoseismology community. Some researchers have suggested that this earthquake, of possible magnitude 7.3, may have caused coastal uplift in the northern Orange County region, with the causative fault being a blind thrust under the San Joaquin Hills (Grant et al., 2002). The nearby Elsinore and Newport-Inglewood faults have also been considered possible sources for the earthquake.

Wrightwood Earthquake of December 12, 1812
This large earthquake occurred on December 8, 1812 and was felt throughout southern California.

Based on accounts of damage recorded at missions in the earthquake-affected area, an estimated magnitude of 7.5 has been calculated for the event (Toppozada et al., 1981). Subsurface investigations and tree ring studies show that the earthquake likely ruptured the Mojave section of the San Andreas fault near Wrightwood, and may have been accompanied by a significant surface rupture between Cajon Pass and Tejon Pass (Jacoby et al., 1988). The worst damage caused by the earthquake occurred significantly west of the San Andreas fault at San Juan Capistrano Mission, where the roof of the church collapsed, killing 40 people. The earthquake also damaged walls and destroyed statues at San Gabriel Mission and damaged missions in the Santa Barbara area. Strong aftershocks caused earthquake-damaged buildings to collapse for several days after the mainshock.

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Table 6-2: Historical (1769 – March 2024) Earthquakes in the Southern California Region with Magnitudes > 4.5
1769 Orange County - Los Angeles Basin 1970 Lytle Creek, east of Mount Baldy 1800 San Diego Region 1971 San Fernando
1812 Wrightwood 1971 San Fernando aftershocks
1812 Santa Barbara Channel 1973 Point Mugu
1827 Los Angeles Region, offshore Malibu 1978 Offshore Santa Barbara 1852 Fort Tejon area, east of Lebec 1981 Offshore, Channel Islands Region 1855 Los Angeles Region 1986 North Palm Springs
1857 Great Fort Tejon Earthquake 1987 Whittier Narrows
1858 San Bernardino Region 1987 Whittier Narrows aftershock 1862 San Diego Region 1988 Between Lebec and Tehachapi
1880 Moreno Valley – Perris Region 1990 Claremont area
1883 West of Frazier Park 1991 North of Pasadena
1889 Mountains north of Morongo Valley 1992 Landers
1892 San Jacinto or Elsinore Fault 1992 Landers aftershocks 1893 Pico Canyon 1992 Big Bear
1894 Lytle Creek Region 1994 Northridge
1894 San Diego Region 1994 Northridge aftershocks
1899 Lytle Creek region 1997 West of Santa Clarita
1899 San Jacinto and Hemet 1999 Hector Mine
1899 San Jacinto and Hemet aftershocks 1999 Hector Mine aftershocks 1905 San Bernardino Region 2001 Anza
1907 San Bernardino Region 2002 Laguna Salada
1910 Glen Ivy Hot Springs 2002 Yorba Linda
1912 Offshore, west of Malibu 2002 Big Bear
1916 Tejon Pass Region 2004 Offshore, south of Coronado 1918 San Jacinto 2004 Arvin
1923 San Bernardino Region 2005 Wheeler Ridge
1925 Santa Barbara 2005 Southeast of Anza
1925 Santa Barbara aftershocks 2005 Yucaipa
1926 Mountains north of Carpinteria 2005 South shores of Salton Sea (Obsidian Butte) 1930 Offshore Malibu 2008 Chino Hills
1930 Seven Oaks Dam area, two events 2009 Bombay Beach swarm 1933 Long Beach 2009 Inglewood
1933 Long Beach aftershocks 2009 Northern Baja California 1935 Mountains north of Morongo Valley 2010 Baja California, South of Mexicali 1938 Santa Ana Mountains 2010 Baja California aftershocks 1940 Mountains north of Northridge 2010 Northwest of Borrego Springs 1941 Carpinteria and Santa Barbara 2012 North of Brawley 1941 Lebec 2012 North of Brawley
1941 Wilmington 2014 La Habra Heights
1943 Big Bear Lake Region 2019 Ridgecrest, two main shocks 1944 Desert Hot Springs – Cabazon Region 2019 Ridgecrest, several aftershocks 1947 Desert Hot Springs – Yucca Valley Region 2019 Searles Valley, several aftershocks 1951 San Clemente Island 2020 Ridgecrest
1952 Tehachapi, Kern County Region 2020 Lone Pine
1952 Tehachapi aftershocks 2021 Imperial County
1954 West of Wheeler Ridge 2023 Ojai
1968 Near Santa Cruz Island 2024 Thousand Oaks
1969 Offshore San Nicolas Island 2024 Malibu, several minor to moderate shocks

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Unnamed Earthquake of December 21, 1812
The Wrightwood earthquake was followed by a strong earthquake on December 21st that caused widespread damage in the Santa Barbara area. The effects of this second earthquake are sometimes attributed to the December 12th event, giving the impression that a single large earthquake caused significant damage from Santa Barbara to San Diego. This second earthquake had an estimated magnitude 7 and was either located offshore, within the Santa Barbara Channel, or it may have occurred inland, in Santa Barbara or Ventura counties. The earthquake destroyed the church at the Mission in Santa Barbara, the Mission of Purísima Concepción near present-day Lompoc, and the Mission at Santa Inéz. The earthquake also caused a tsunami that may have traveled up to 1/2 mile inland near Santa Barbara.

Unnamed Earthquake of 1855
This earthquake occurred on July 11, 1855 and was felt across southern California from Santa Barbara to San Bernardino. Light to moderate damage was reported in the Los Angeles area, where 26 houses experienced cracked walls and the bell tower of the San Gabriel Mission was knocked down. Because damage was limited primarily to the Los Angeles area, this earthquake is postulated to have occurred on a local fault such as the Hollywood-Raymond, Whittier or Newport-Inglewood faults, or on one of the many blind thrust faults that underlie this area.

Santa Monica Earthquake of 1930
This ML (Richter magnitude) 5.2 earthquake occurred in Santa Monica Bay on August 31, 1930, at 4:40 P.M. PST0F
1 . Using station delays calculated from the 1979 Malibu earthquake (ML 5.0), Hauksson and Saldivar (1986) revised the location of the 1930 earthquake to near the western end of the Santa Monica fault, approximately 1 mile offshore of the eastern Malibu coast. The earthquake produced moderate to strong shaking (Modified Mercalli Intensities of V-VI) at some locations in the Los Angeles basin and San Fernando Valley (Gutenberg et al., 1932). Unusually high intensities were also recorded to the east, in Riverside (MMI V), San Jacinto (MMI IV), and Hemet (MMI IV), located approximately 100 miles away from the epicenter (Gutenberg et al., 1932; Hauksson and Saldivar, 1986).

Long Beach Earthquake of 1933
This Mw 6.4 earthquake occurred on March 10, 1933, at 5:54 P.M. PST, following a strong foreshock the day before. The earthquake’s epicenter was offshore of Newport Beach, approximately 3 miles south of present-day Huntington Beach, on the Newport-Inglewood fault (see Figure 6.4). However, because extensive damage was reported in Long Beach, the earthquake is referred to as the Long Beach earthquake. The earthquake caused 120 deaths, and over $50 million (~$1.20 billion in 2024) in property damage (Wood, 1933). Many strong aftershocks occurred through March 16th.
1 PST stands for Pacific Standard Time, and it is the North American time zone in the western United States, including California, that is eight hours behind Coordinated Universal Time (UTC). Since 2006, PST starts on the first Sunday in November and extends to the second Sunday in March. Pacific Daylight Time (PDT), which is seven hours behind UTC (UTC – 7:00), is used during the remainder of the year. Between 1967 and 2006, PST changed to PDT on the first Sunday in April and reversed back to PST on the last Sunday in October. PDT was first used in the U.S. in 1918, during the first world war, and occasionally, in a hodge-podge manner. California has used PDT since 1954. Earthquake catalogs typically report earthquakes in UTC time to avoid confusion caused by local time zones.

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Although primary ground rupture of the Newport-Inglewood fault was not observed, secondary cracking, minor slumping, and lateral movement of unconsolidated sediments occurred throughout the region. Road surfaces along the shore between Long Beach and Newport Beach were damaged by settlement of road fills that had been placed on marshy land. In urban areas, unreinforced masonry buildings were most severely damaged, especially in areas of artificial fill or water-saturated alluvium. In one part of Compton, most buildings built on unconsolidated sediments and artificial fill were destroyed. In Long Beach, many buildings collapsed, were pushed off their foundations, or had walls or chimneys knocked down. In Newport Beach, 800 chimneys were knocked down at the roofline and hundreds of houses were destroyed. As a result, building codes were improved. Damage to school buildings was especially severe; fortunately, children were not present in the classrooms at that time, otherwise, the death toll would have been much higher. This earthquake led to the passage of the Field and Riley Acts by the State legislature. The Field Act regulates school construction, and gives the Division of the State Architect authority and responsibility for approving the design and supervising the construction of public schools. The Riley Act regulates the construction of buildings larger than two-family dwellings.

Torrance-Gardena Earthquakes of 1941
In 1941, two small earthquakes struck the southern Los Angeles basin, affecting surrounding communities. Although these earthquakes were relatively minor, they occurred close to the surface and caused significant, although localized damage. The first Torrance earthquake (with a magnitude of 4.7) occurred on October 21st at 10:57 P.M. PST, and was located east of Carson, near the present-day interchange of the 405 and 710 freeways. Shaking up to intensity level VII was reported in the communities of Wilmington, Gardena, Lynwood, Hynes and Signal Hill where walls were cracked and chimneys damaged. In some cases, houses that had not been adequately repaired after the 1933 Long Beach earthquake were damaged again. No injuries were reported and damage estimates totaled $100,000 (~$2.1 million in 2024).

A second earthquake (of magnitude 5.1) occurred less than a month later, on November 14 at 12:42 A.M. PST, near Wilmington. Shaking during the second earthquake was reportedly stronger than the first, locally reaching intensity level VIII (Table 6-1) and felt as far away as Cabazon, Carpinteria, and San Diego. Gas and water mains burst near the epicenter and storefronts in the business districts of Torrance and Gardena collapsed, crushing parked cars. Damage to local oilfields was significant –- well casings and equipment were damaged and a 55,000-gallon oil tank ruptured, flooding nearby streets with oil. Production of several wells was lowered or stopped. No injuries were reported, although damage attributed to the second event was estimated at $1 million (~$21.1 million in 2024).

San Fernando (Sylmar) Earthquake of 1971
This Mw 6.6 earthquake occurred on the San Fernando fault zone, the western-most segment of the Sierra Madre fault, on February 9, 1971, at 6:00 A.M. PST. The surface rupture caused by this earthquake was nearly 12 miles long, and occurred in the Sylmar-San Fernando area, approximately 24 miles (38 km) northwest of Santa Monica. The maximum slip measured at the surface was nearly 6 feet.

The earthquake caused over $38.3 million in property damage (~$500 million in 2024) and 65 deaths. Most of the deaths occurred when the Veteran's Administration Hospital in Sylmar collapsed. Several other hospitals, including the Olive View Community Hospital in Sylmar suffered severe damage. Newly constructed freeway overpasses also collapsed, in damage scenes

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similar to those that occurred 23 years later during the 1994 Northridge earthquake. Loss of life could have been much greater had the earthquake struck at a busier time of day. As with the Long Beach earthquake, legislation was passed in response to the damage caused by the 1971 earthquake. In this case, the building codes were strengthened and the Alquist Priolo Special Studies (now known as the Earthquake Fault Zone) Act was passed in 1972.

Point Mugu Earthquake of 1973
This magnitude 5.3 earthquake occurred on the Malibu Coast fault, the westernmost segment of the Malibu Coast-Santa Monica-Hollywood fault zone, on February 1, 1973, at 6:46 A.M. PST. The Point Mugu earthquake was responsible for at least five injuries and more than $1 million in damage ($7 million in 2024 dollars) in the Point Mugu-Oxnard area, although damage was mainly confined to the epicentral area (https://scedc.caltech.edu/earthquake/pointmugu1973.html). Large boulders fell down onto Highway 1 at Point Mugu, partially blocking the road. Over 7,000 customers were without electricity for hours. Most damage reported was to windows, ceilings, plaster, chimneys and shelved goods, but structural damage and broken pipes were also reported.

Malibu Earthquake of 1979
This magnitude 5.2 earthquake occurred on January 1, 1979, at 3:15 P.M. PST, along the AnacapaDume fault. The Anacapa-Dume fault is located approximately 3.2 km (2 mi) offshore the Malibu coast, and it is separated from the Santa Monica fault by a 5- to 6-mi (8- to 9.7 km) north-south sidestep (Hauksson and Saldivar, 1986). The 1979 Malibu earthquake caused only minor damage in the areas closest to the epicenter, although it was felt as far away as Kings, Kern, and San Diego counties (https://scedc.caltech.edu/earthquake/malibu1979.html). Stover et al. (1980) reported intensities of VI (along the Malibu coast and at several sites in the San Fernando Valley. Moderate to strong shaking (MMIs of V-VI) was felt in the Santa Monica area.

Whittier Narrows Earthquake of 1987
The Whittier Narrows earthquake occurred on October 1, 1987, at 7:42 P.M. PST, (Hauksson and Jones, 1989), with its epicenter located approximately 20.5 miles (33 km) to the east of Santa Monica. This magnitude 5.9 earthquake occurred on a previously unknown, north-dipping concealed thrust fault (blind thrust) now called the Puente Hills fault (Shaw and Shearer, 1999).

Modified Mercalli intensities in the VII to VIII range were reported from Monrovia and Pasadena in the north, to beyond Whittier in the southeast. Modified Mercalli intensities in the VI range were reported farther out, in an approximately 580-square-mile area.

The earthquake caused eight fatalities, over 900 injured, and $358 million (~$978 million in 2024) in property damage. Severe damage was confined mainly to communities east of Los Angeles and near the epicenter. Areas with high concentrations of unreinforced masonry (URM) buildings, such as the “uptown” district of Whittier, the old downtown section of Alhambra, and the “Old Town” section of Pasadena, were severely impacted. Several tilt-up buildings partially collapsed, including tilt-up buildings built after 1971, that were built to meet improved building standards, but were of irregular configuration, revealing seismic vulnerabilities not previously recognized.

Residences that sustained damage usually were constructed of masonry, were not fully anchored to their foundations, or were houses built over garages with large openings. Many chimneys collapsed, and in some cases, fell through roofs. Wood-frame residences, in contrast, sustained relatively little damage, and no severe structural damage was reported to high-rise structures in downtown Los Angeles.

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Malibu Earthquake of 1989
This magnitude 5.0 earthquake occurred on January 18, 1989, at 10:53 P.M. PST. This earthquake is spatially associated with the Palos Verdes-Shelf Projection anticlinorium, a fold broadly located offshore in the Santa Monica Bay (Sorlien et al., 2004). As a result of the shaking caused by this earthquake, several people were injured, shelved items fell in local stores, and some windows broke. Hardest hit was the coastal region encompassing Malibu, Santa Monica, and Redondo Beach, although damage was low even in that area
(https://scedc.caltech.edu/earthquake/chronological.html). Slight damage was also reported in Los Angeles, Hollywood, Monterey Park, and as far away as Lancaster.

Landers and Big Bear Earthquakes of 1992
On the morning of June 28, 1992, most people in southern California were awakened at 4:57 A.M. by the largest earthquake to strike California in 40 years. Named “Landers” after a small desert community near its epicenter, the earthquake had a magnitude of 7.3. Centered in the Mojave Desert, approximately 120 miles from Los Angeles, the earthquake caused relatively little damage for its size (Brewer, 1992). It released about four times as much energy as the very destructive Loma Prieta earthquake of 1989, but fortunately, it did not claim as many lives (one child died when a chimney collapsed). The power of the earthquake was illustrated by the length of the ground rupture it left behind. More than 50 miles of surface rupture occurred as a result of this earthquake. The earthquake ruptured five separate faults: Johnson Valley, Landers, Homestead Valley, Emerson, and Camp Rock faults (Sieh et al., 1993). Other nearby faults also experienced triggered slip and minor surface rupture. The average right-lateral strike-slip displacement was about 10 to 15 feet, with a maximum of up to 18 feet observed. Modified Mercalli Intensities of between V and VI were retroactively reported to the U.S. Geological Survey’s “Did You Feel It?” application by Santa Monica residents as a result of this earthquake.

The magnitude 6.4 Big Bear earthquake struck little more than 3 hours after the Landers earthquake on June 28, 1992 at 8:05:30 A.M. PST. This earthquake is technically considered an aftershock of the Landers earthquake (indeed, the largest aftershock), although the Big Bear earthquake occurred over 20 miles west of the Landers rupture, on a fault with a different orientation and sense of slip than those involved in the main shock. From its aftershock, the causative fault was determined to be a northeast-trending left-lateral fault. The Big Bear earthquake did not break the ground surface, and, in fact, no surface trace of a fault with the proper orientation has been found in the area. The Big Bear earthquake caused a substantial amount of damage in the Big Bear area, but fortunately, it claimed no lives. However, landslides triggered by the quake blocked roads in the mountainous areas, aggravating the clean-up and rebuilding process.

Northridge Earthquake of 1994
The Northridge Earthquake of January 17, 1994 woke up most of southern California at 4:30 in the morning. The earthquake’s epicenter was located 20 miles to the west-northwest of downtown Los Angeles, on a previously unknown blind thrust fault now called the Northridge Thrust. Although moderate in size, this earthquake produced the still-strongest ground motions (1.2g horizontal and

1.0g vertical) instrumentally recorded in an urban setting in the United States (https://scedc.caltech.edu/earthquake/northridge1994.html).

The Mw 6.7 earthquake is one of the most expensive natural disasters to have impacted the United States, with $20 billion ($41.9 billion in 2024 dollars) in property damage and more than $40

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billion ($83.8 billion in 2024) in economic losses. Damage was widespread, sections of major freeways, parking structures and office buildings collapsed, and numerous apartment buildings suffered irreparable damage. Damage to wood-frame apartment houses was very widespread in the San Fernando Valley and Santa Monica areas, especially to structures with "soft" first floor or lower-level parking garages. The high accelerations, both vertical and horizontal, lifted structures off of their foundations and/or shifted walls laterally. Up to 72 people died, and more than 1,500 people were seriously injured.

The Santa Monica area was hit particularly hard, in part because the seismic waves were focused along and bounced back from shallow sections of bedrock along the Santa Monica fault (Bausch and Gonzalez, 1994; Graves et al., 1998; Davis et al., 2000). The earthquake affected almost every building on the Santa Monica College campus, with extensive damage also reported at the Santa Monica Hospital Medical Center, Saint John’s Hospital, and St. Monica’s Catholic Church.

Both hospitals experienced significant damage, with sections of the buildings closed for months for repairs. The north wing of Saint John’s had to be demolished. More than 1,600 housing units were damaged, and a section of the I-10 freeway across Centinela Boulevard collapsed, making travel into and out of the city difficult. Following the earthquake, Santa Monica issued more than 3,400 repair permits for earthquake-damaged properties, and fifty-three (53) buildings were demolished because they were determined to be damaged too extensively. Despite the losses, gains made through earthquake hazard mitigation efforts implemented during the previous two decades, including retrofits of masonry buildings, helped reduce the loss of life. Strengthening of hospitals following the 1971 San Fernando earthquake also helped.

Hector Mine Earthquake of 1999
Widely felt magnitude 7.1 event that occurred on October 18, 1999 in a remote region of the Mojave Desert, 47 miles east-southeast of Barstow. The Hector Mine earthquake occurred on a series of north-northwest trending strike-slip faults within the Eastern Mojave Shear Zone.

Geologists documented a 25-mile (40-km) long surface rupture and a maximum right-lateral strikeslip offset of about 16 feet on the Lavic Lake fault. Surface rupture was confined entirely within the Twentynine Palms Marine Corps Base, and did not extend across any paved roads or buildings. As a result, the earthquake caused very little damage to structures or infrastructure; the most significant damage reported was the derailment of an Amtrak train.

Baja California Earthquake of 2010
A magnitude 7.2 earthquake that occurred just south of the U.S. / Mexico border on Easter Sunday, April 4, 2010, at 3:40:42 PM PST, was felt throughout Mexico, southern California, Arizona, and Nevada. Based on analysis of the waveforms, seismologists identified two sub-events: one rupturing an 18-km section of the Pescadores fault, followed, six to 12 seconds later by a second, larger event on the Borrego fault. Both of these faults are part of the Laguna Salada fault system, which is the southern extension of the Elsinore fault. Surface rupture continued northward to just past the border into California. The main earthquake caused triggered slip of up to a few centimeters on several faults in the Salton Sea area, and as far north as in the Mecca Hills.

Secondary effects, including liquefaction, rockfalls and shattering were reported along a wide area in the El Centro and Brawley region, and westward toward San Diego. More than 4,000 aftershocks were recorded within the first ten days after the main shock, and more than 9,500 were recorded in the two months after the main event (Kroll et al., 2013). A peak instrumental ground acceleration of 1.1g was recorded at the Salton Sea. Similar or stronger shaking may have occurred closer to the epicenter, but given the lack of instrumentation in that area, went

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unrecorded. Many of the aftershocks occurred along the Elsinore, San Jacinto, and the southern extension of the San Andreas fault through the Brawley area. Based on observations reported by many residents, shaking in the Santa Monica area as a result of this earthquake was light, in the Modified Mercalli intensity III range
(https://earthquake.usgs.gov/earthquakes/eventpage/ci14607652/map).

Ridgecrest Earthquake Sequence of 2019
The Ridgecrest sequence in eastern California included two moderate (Mw>6) earthquakes and thousands of relatively small (Mw<6) earthquakes on a previously unnoticed section of the Little Lake Fault Zone southwest of Searles Valley. The first moderate earthquake (Mw6.4) occurred on July 4th, 2019, at 10:33 A.M. PDT, whereas the second moderate earthquake (Mw7.1) occurred on July 5th, 2019, at 8:19 P.M. PDT. The damage was most severe close to the epicenter, near the town of Ridgecrest, where buildings, roads, and public utility lines were damaged. Shaking was widely felt throughout California, including light to moderate ground shaking in Los Angeles, weak shaking in the San Francisco Bay Area, and some minor but noticeable shaking as far east as Phoenix, Arizona and as far north as Sacramento. In the Santa Monica area, shaking felt on July 5th as a result of the Mw 7.1 Ridgecrest earthquake resulted in MMI levels between III and IV (https://earthquake.usgs.gov/earthquakes/eventpage/ci38457511/dyfi/intensity).

Ojai Earthquake of 2023
This M 5.1 earthquake occurred on August 20, 2023 at about 2:45 PM local time, the same day coastal southern California was being battered by the remains of Tropical Storm Hilary. The epicenter was approximately 4 miles southeast of Ojai, in Ventura County, and was felt throughout the region. Shaking near the epicenter was reported in the MMI levels of between V and VI. In Santa Monica and greater Los Angeles region, shaking was reported in the MMI range of III to IV (https://earthquake.usgs.gov/earthquakes/eventpage/ci39645386/dyfi/intensity). The main quake was preceded by several foreshocks, and aftershocks were felt several days after.

EARTHQUAKE HAZARD ASSESSMENT
Choosing Earthquakes for Planning and Design
It is often useful to create a design earthquake scenario to study the effects of a particular earthquake on a building or a community. Typically, such scenarios have considered the largest earthquake believed possible to occur on a fault or fault segment, referred to as the maximum magnitude earthquake (Mmax). Building codes usually consider other scenarios for the design of structures, using the ground motion with a statistical probability of being exceeded in a given length of time, with different earthquake scenarios considered depending on the application, such as the planned use, lifetime, or importance of a facility. Traditionally, the more critical the structure, the longer the time period used between earthquakes and the larger the design earthquake that has been used. Seismic design parameters in the most recent version of the California Building Code (2023 edition) are based on the risk-targeted maximum considered earthquake, with a ground motion that has a 2 percent probability of being exceeded in 50 years and a recurrence interval of about 2,500 years, with an adjustment for risk. Risk is defined as the probability that damage will occur to the proposed structure. Seismic design parameters define what kinds of earthquake effects a structure must be able to withstand. These include peak ground acceleration, duration of strong shaking, the periods of incoming strong motion waves, and the orientation of maximum response of the earthquake’s motion.

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Geologists, seismologists, engineers, emergency response personnel and urban planners typically have used maximum magnitude and maximum considered earthquakes to evaluate the seismic hazard of a site or area. The assumption is that if we plan for the worst-case scenario, we establish safety margins. As a result, smaller earthquakes, which are more likely to occur, can be dealt with effectively.

As is true for most of the Los Angeles Basin, many potential earthquake sources pose a threat to Santa Monica (see Table 6-1). Thus, it is also important to consider the overall likelihood of damage from a plausible suite of earthquakes. This approach is called probabilistic seismic hazard analysis (PSHA), and typically considers the likelihood of exceeding a certain level of damaging ground motion that could be produced by any or all faults within a 100-km (62-mile) radius of the project site, or in this case, the city of Santa Monica.

In California, many agencies are focused on seismic safety issues, including the California Geological Survey (CGS), the State’s Seismic Safety Commission (SSC), the Governor’s Office of Emergency Services (OES), the Applied Technology Council (ATC), and the California Institute of Technology (Cal Tech). A number of other universities and private foundations also invest time and resources in seismic studies and seismic hazard mitigation. Many of these organizations, often in partnership with other State and Federal agencies such as the U.S. Geological Survey and FEMA, have undertaken a rigorous program in California to identify seismic hazards and risks, including active fault identification, ground shaking, ground motion amplification, liquefaction, earthquake induced landslides, and for coastal areas, tsunami inundation zones. Seismic hazard maps that identify areas thought to be susceptible to earthquake-induced fault rupture, liquefaction, slope failures, and tsunamis, have been published and are available for many communities in California through the California Geological Survey. This report refers to several of these maps to discuss the most significant earthquake-induced hazards with the potential to impact the city of Santa Monica. These hazards are described below and in other pertinent sections of this document.

Seismic Shaking
Seismic shaking is the seismic hazard that has the greatest potential to severely impact Santa Monica given the city’s proximity to several active seismic sources (faults). To give the City a better understanding of the hazard posed by these faults, we compiled, using a series of ShakeMaps prepared by the U.S. Geological Survey (USGS) Earthquake Hazards Program, the peak horizontal ground accelerations (PHGA) and Modified Mercalli intensities (MMIs) anticipated in the city as a result of an earthquake on several of the known Holocene-active faults within about 62 miles (100 km) from Santa Monica. The ShakeMap scenarios use realistic assumptions about the size and location of a future earthquake to estimate its impact in the epicentral area; this information is in turn used for loss estimations, preparedness exercises and disaster planning. The distances between the faults and the city were measured using the Community Fault Model (CFM, version

6.0) by the Southern California Earthquake Center (SCEC; Marshall et al., 2022).

Peak ground acceleration (ground shaking) depends on the size of the earthquake (which is in turn dependent in the dimensions of the ruptured fault plane), the proximity of the rupturing fault, and local soil conditions. Effects of soil conditions are estimated using attenuation relationships developed from empirical data. Specifically, to develop these relationships, scientists analyze recordings of earthquake shaking on similar soils during earthquakes of various sizes and distances. The peak ground acceleration estimates obtained from these analyses can be then used

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to provide a general indication of relative earthquake risk at a given site. For individual projects however, site-specific analyses that consider the precise distance from a given site to the various faults in the region, as well as the local near-surface soil types, should be conducted.

The PGAs and intensities listed on Table 6-3 below should be considered as approximate values, as different areas of Santa Monica are expected to feel and respond to each earthquake differently in response to site-specific conditions. These conditions may include the geometry of the basin and the possible reflection, and amplification, of the seismic waves off the harder rock forming the Santa Monica Mountains to the north. The models may not consider some of these local conditions, and as a result, localized higher accelerations than those listed here are possible.

Moreover, please note that the PGA values listed on Table 6-3 provide a general indication of relative earthquake risk throughout the Santa Monica area, but these values are not to be used for building design purposes.

Table 6-3 shows:
• The closest approximate distance, in miles and kilometers, between each of the faults listed and various points in the Santa Monica region, given as a range. Since these measurements are based on specific, but randomly selected points in the study area; other points in the city could be closer or farther away from the faults than the distances provided herein; • the maximum magnitude earthquake (Mmax) each fault is estimated capable of generating; • the range in peak ground accelerations (PGAs) expressed as a fraction of the acceleration of gravity (g), that could be experienced in the Santa Monica area if the Mmax occurs on one of these faults (values given range from the median to median plus 1 sigma standard deviation); and
• the range in Modified Mercalli seismic Intensity (MMI) values estimated to be felt in the city as a result of the Mmax on each one of these faults.

Those faults that can cause peak horizontal ground accelerations of about 0.1g or greater (Modified Mercalli Intensities greater than VII) in the Santa Monica area are listed in Table 6-3. For a map showing most of these faults, refer to Figures 6-1 and 6-4. Those faults included in Table 6-3 that would have the greatest impact on the Santa Monica area, or that are thought to have a higher probability of causing an earthquake, are described in more detail in the following pages.

The PGA and MMI values extracted from USGS ShakeMaps indicate that many nearby faults, such as the Santa Monica, Malibu Coast, Compton blind thrust, Hollywood, Palos Verdes, NewportInglewood, Anacapa-Dume, and Puente Hills blind thrust, have the potential to generate severe to extreme ground shaking in the city of Santa Monica. The worst-case scenario event would likely result from rupture of the Santa Monica fault together with the Malibu Coast fault to the west and the Hollywood fault to the east in an estimated Mw 7.4 earthquake. This potential scenario would create extreme perceived shaking in the Santa Monica area, with potential PGA values ranging from about 0.3g to more than 0.75g (compare Tables 6-1 and 6-3). Shaking at these levels can cause significant damage to older structures, and moderate damage to even newer buildings constructed in accordance with the latest building code provisions.

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Table 6-3: Estimated Horizontal Peak Ground Accelerations and Seismic Intensities in the Santa Monica Area
0BFault Name or Fault Zone
Distance to
Santa Monica
β (km)
Distance to
Santa Monica
β (mi)
Magnitude
of Mmax*
PGA (g)
from Mmax*
MMI
from Mmax*
Santa Monica rupturing together with
the Malibu Coast and Hollywood faults 0 – 12 0 – 7.5 7.4 0.75+ – 0.3 VIII+
Santa Monica 0 – 4 0 – 2.5 6.8 0.65 – 0.2 VIII – VII
Malibu Coast 2 – 10 1 – 6 7.0 0.65 – 0.3 VIII – VII+
Anacapa-Dume 3.5 – 10.5 2 – 6.5 7.2 0.75+
– 0.2 VIII+ – VII
Newport-Inglewood (Onshore) 5 – 16 3 - 10 7.2 0.75+
– 0.2 VIII+ – VII
Hollywood 7 – 12 4 – 7.5 6.7 0.35 – 0.2 VII – VI
Compton Blind Thrust 11 - 18 6.8 - 11 7.5 0.63+ VIII+ – VIII Palos Verdes 11 – 23 7 – 14.5 7.7 0.75+
– 0.2 VIII+ – VII
Upper Elysian Park Thrust 18 – 24 11 – 15 6.7 0.35+
– 0.1 VII+ – VI
Puente Hills (Los Angeles segment) 11 – 19 7 – 12 7.0 0.35+ – 0.1 VII+ – VI
Puente Hills (Santa Fe Springs segment) 31 – 39 19.5 – 24 6.7 0.2+ – 0.1 VI+
Puente Hills (Coyote Hills segment) 40 – 47 25 – 29 6.9 0.3 – 0.1 VII – VI Raymond 21 – 27 13 – 17 6.8 0.2+
– 0.1 VI+
Verdugo 23 – 29 14 – 18 6.9 0.2+
– 0.1 VI+
Sierra Madre 37 – 43 23 – 26 7.2 0.2+
– 0.1 VI+
San Andreas;
Shakeout2 Full Scenario 67 – 104 41 – 65 7.8 0.2 – 0.05 VI – V San Jacinto fault rupture consisting of
San Bernardino + San Jacinto Valley
+ Anza + Clark Segments
101 – 108 63 – 67 7.7 0.2 – 0.05+ VI – V+
Notes and Abbreviations used in Table 6-3:
β Distances measured from the Community Fault Model (CFM, version 6.0) by the Southern California Earthquake Center (SCEC; Marshall et al., 2022). For the blind faults, the distances indicated are to the surface projection of the fault ramp and/or, in the case of the Compton fault, to the fault at depth under Santa Monica. * Data from USGS ShakeOut Scenarios (https://earthquake.usgs.gov/scenarios/catalog/sclegacy/). The peak ground accelerations and MMI values are listed from high to low in an effort to show that locations closer to the fault will experience the higher peak ground accelerations and stronger shaking. mi – miles; km – kilometer; Mmax – magnitude of the largest earthquake the fault is thought capable of generating, based on its length; PGA – peak ground acceleration as a percentage of g, the acceleration of gravity; MMI – Modified Mercalli Intensity.

The ground motions presented in Table 6-3 are based on the largest earthquake that each fault, or fault segment, is believed capable of generating, referred to as the maximum magnitude earthquake (Mmax). This deterministic approach is useful to study the effects of a particular earthquake on a building or community. However, because many potential earthquake sources pose a hazard to the region, it is also important to consider the overall likelihood of damage from a plausible suite of earthquakes, including earthquakes of different sizes on the same fault. This approach is called probabilistic seismic hazard analysis (PSHA), and typically considers the

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likelihood of exceeding a certain level of damaging ground motion that could be produced by any or all faults within a given radius of the study area, which in this case is the city of Santa Monica.

Most seismic hazard analyses consider a distance of 100 km (62 miles), but this is arbitrary.

PSHA is used by the USGS to produce national and state seismic hazard maps for risk assessment, such as those used by the Uniform Building Code and the California Building Code. Specifically, the Unified Hazard Tool is a PSHA platform developed and maintained by the National Seismic Hazard Mapping Project (NSHMP) within the USGS earthquake hazards program that computes the statistical likelihood of an earthquake occurrence in terms of PGA (https://earthquake.usgs.gov/hazards/interactive/). This analysis differs from ShakeMaps because the computed PGA is based on the combined effects of multiple seismic sources.

The Unified Hazard Tool using the “Dynamic: Conterminous U.S. 2014 (update) (v.4.2.0)” edition was utilized to estimate the ground motions in the city of Santa Monica that have a 10% probability of exceedance in 50 years (equivalent to a return period of ∼475 years), and a 2% probability of exceedance in 50 years (equivalent to a return period of ∼2,475 years1F 2 ). Site class
“C/D boundary” for soils with a shear wave velocity in the upper 100 feet (30 m) of approximately 1,200 feet per second (equivalent to 365 meters per second [m/sec]) was selected for the analysis based on data obtained from the CGS2F
3 . The Unified Hazard Tool estimated levels of ground
motion for Santa Monica with a 10% and a 2% probability of being exceeded in 50 years of approximately 0.51g and 0.93g, respectively. The principal sources responsible for these levels of shaking are the Palos Verdes fault, the various faults of the Malibu Coast-Santa Monica-Hollywood fault system, the Newport-Inglewood fault zone, and the Compton blind thrust. These levels of shaking correspond to Modified Mercalli Intensity values of VIII to IX, and can be expected to cause significant damage, particularly to older and poorly constructed buildings. The maximum considered earthquake geometric mean PGA adjusted for site effects using the ASCE Tool 7-223F 4 ,
and a stiff soil (soil class C/D; for soils with shear wave velocities of 365 m/sec), returned a value for Santa Monica of 0.91g, nearly the same as the 2% in 50-years PGA value calculated using the Unified Hazard Tool.

Seismic Shaking Sources
Santa Monica Fault
The Santa Monica segment is a north-dipping, high angle fault that extends for a distance of approximately 25 miles (40 km) through the communities of Beverly Hills, Westwood, Santa Monica, and Pacific Palisades, before going offshore parallel to the Malibu coastline. The Santa Monica fault is one segment of a much longer system of faults, referred to as the Southern Frontal Fault System, that forms the southern boundary of the Transverse Ranges geomorphic province.

From west to east these faults include the Malibu, Anacapa–Dume, Santa Monica, Hollywood and Raymond (Figure 6-1). These individual fault segments are discussed in the following subsections.

Specifics regarding the Santa Monica fault as it pertains to its location through the city of Santa Monica and its hazard of surface fault rupture are also discussed later in this section.

2 Seismic design parameters in the 2022 California Building Code are based on the maximum considered earthquake, which is an earthquake that is expected to occur once in approximately 2,475 years. 3 Based on California Geological Survey (CGS) Map Sheet 48: Shear-wave Velocity in Upper 30m of Surficial Geology (Vs30) available from https://gis.data.ca.gov/datasets/cadoc::cgs-map-sheet-48-shear-wave-velocity-inupper-30m-of-surficial-geology-vs30/explore?location=34.027555%2C-118.483092%2C13.66, accessed on October 26, 2023. 4
https://asce7hazardtool.online/; accessed on October 26, 2023 and March 18, 2024.

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A limited paleoseismic study of the Santa Monica fault at the West Los Angeles Veteran’s Health Administration (VA) Medical Center just one mile east of Santa Monica suggests that the fault has experienced two to three surface-rupturing events in the last 16,000 to 17,000 years (the most recent event probably occurred between 1,000 and 3,000 years ago), and at least six rupture events in the past about 50,000 years (Dolan and others, 2000c). Based on these data, the rate of slip on the Santa Monica fault is poorly constrained, but is estimated at between 0.5 and 1.5 mm/yr (Dolan and others, 1995; Dolan and others, 2000c).

Given its length, rupture on the Santa Monica fault on its own is thought capable of generating a magnitude 6.8 earthquake. Such an earthquake would result in PGAs of between about 0.2g and

0.65g in Santa Monica (Table 6-3). If the Santa Monica fault ruptures together with the Malibu Coast fault to the west and the Hollywood fault to the east, an earthquake as large as Mw7.4 is possible. Such an earthquake could produce peak ground accelerations in excess of 0.75g and cause moderate to severe damage to many structures in the city of Santa Monica. The ShakeMap for a magnitude 7.4 earthquake scenario on the combined Malibu Coast–Santa Monica– Hollywood fault system is shown on Figure 6-5. Note that Modified Mercalli intensities in the city as a result of this scenario earthquake are expected to exceed VIII.

Malibu Coast Fault
The Malibu Coast fault is a complex zone of reverse and left-stepping, en echelon4F 5 , left-lateral
strike-slip faults that parallel the west-trending coastline in the Malibu area of southern California.

The onshore traces of the fault zone are moderately well expressed by an alignment of benches, saddles and linear drainages, but youthful landsliding and erosion make it difficult to determine the fault’s recency of activity. The offshore section of the fault zone is not well defined.

The Malibu Coast fault is known to have moved in the late Quaternary, with the timing of the most recent surface-rupturing earthquake on this fault being poorly constrained. Treiman (1994) reported no evidence for Holocene displacement along most of the onshore fault traces. Probable Holocene displacement was reported on one, and possibly two, secondary faults (Drumm, 1992; Rzonca and others, 1991), but later studies indicated that some of these secondary faults have not moved in the past 11,000 years (Leighton and Associates, 1994a; Earth Consultants International, 2000; 2002). These data suggest that many of the Malibu Coast fault traces onshore either are no longer active, or they move very infrequently. Treiman (1994, 2000) favored the first alternative, suggesting that the slip rate of the fault has diminished from about 1 to 2 mm/yr in the Quaternary, to 0.5 mm/yr in the late Quaternary, to nearly zero in the Holocene. Alternatively, the active strands of the fault may have moved southward (and beachward), analogous to several other range-fronting faults such as the Sierra Madre and Cucamonga faults. Further studies are necessary to resolve these questions.

Nevertheless, the Malibu Coast fault is included in both the Uniform California Earthquake Rupture Forecast, Version 3 (UCERF3; Field and others, 2013) and the California Fault Model, Version 6.1 (Marshall et al., 2022) databases, albeit with a preferred relatively low slip rate of about 0.3 mm/yr. As a result, the fault is also considered in this analysis. Given its length, the Malibu Coast fault is thought capable of generating a magnitude 7.0 earthquake. An earthquake of that size on this fault is estimated to cause ground shaking in the Santa Monica area with PGAs between 0.3g and 0.65g, with MMI values in the VII to VIII range.

5 En echelon refers to closely spaced parallel or subparallel, overlapping or step-like features

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Figure 6-5: ShakeMap for a Magnitude 7.4 Earthquake Scenario on the Malibu Coast–Santa Monica–Hollywood Fault System
Source:
https://earthquake.usgs.gov/scenarios/eventpage/sclegacysantamonicaconnectedalt2m7p4_se/shakemap/intensity Anacapa-Dume Fault
The Anacapa-Dume fault is an offshore fault that is poorly studied. Some researchers suggest that the Anacapa and Dume faults are separate structures, with the Anacapa fault being a segment of the Malibu Coast fault, and the Dume fault being a possible extension of the Santa Monica fault.

As traditionally mapped, the Anacapa-Dume fault is thought to be a left-lateral oblique fault approximately 47 miles (75 km) long that is receiving slip from both the Palos Verdes and Santa Monica faults. UCERF3 (Field et al., 2013) assign it a preferred slip rate of 0.39 mm/yr, with minimum and maximum slip rate estimates of 0.2 and 1.0 mm/yr, respectively. Given its length, the fault is thought capable of generating a magnitude 7.2 earthquake. Such an earthquake would generate PGAs in the Santa Monica area of about 0.2 to 0.75+ g, with MMIs in the VII to VIII+
range. Future studies of this fault system are likely to modify significantly our current understanding of this fault, which may require a revision to this section of the report when it is updated.

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Hollywood Fault
The Hollywood fault is the eastern 9-mile (14 km) long segment of the Malibu–Santa Monica– Hollywood fault system that forms the southern margin of the Santa Monica Mountains (locally known as the Hollywood Hills). It has also been considered the westward extension of the Raymond fault. Movement on the Hollywood fault over geologic time is thought responsible for the growth of the Hollywood Hills, which is why earlier researchers characterized this fault as a northward-dipping reverse fault. However, studies by Dolan et al. (1997, 2000a) and Tsutsumi et al. (2001) showed that the Hollywood fault is primarily a left-lateral strike-slip fault, consistent with its linear trace and steep, 80- to 90-degree dips (reverse faults typically have irregular, arcuate traces and shallow dips).

The Santa Monica–Hollywood fault system has not produced any damaging historical earthquakes and it has had only relatively minor microseismic activity. Subsurface studies by Dolan et al. (2000a) suggest that the Hollywood fault moves infrequently. The most recent surface-rupturing earthquake on this fault appears to have occurred 7,000 to 9,500 years ago, and another earthquake appears to have occurred between about 10,000 and 22,000 years ago (Dolan et al., 2000a). These data suggest that the fault either has a slow rate of slip (of between 0.33 and 0.75 mm/yr), or that it breaks in infrequent but large-magnitude earthquakes. UCERF3 (Field and others, 2013), assigns this fault a preferred slip rate of 0.9 mm/yr, with minimum and maximum rates of

0.2 and 1.5 mm/yr, respectively.

Based on its length, the Hollywood fault is thought capable of generating a Mw ~6.4 to 6.7 earthquake. A magnitude 6.7 earthquake on the Hollywood fault is thought capable of generating PGAs of about 0.2g to 0.35g in Santa Monica, with MMIs of VI to VII.

Palos Verdes Fault
The Palos Verdes fault zone is located primarily offshore, extending in a southeasterly direction from Santa Monica Bay to its possible connection with the Coronado Bank fault zone at about the latitude of La Jolla in San Diego County, a distance of more than 68 miles (110 km). The fault extends onshore a short distance, between Redondo Beach and San Pedro, and follows the northeastern flank of the Palos Verdes Hills, along the southern limits of the city of Torrance. The fault accommodates both right-lateral strike-slip and reverse dip-slip motion, with some segments experiencing primarily strike-slip movement, whereas other sections, like the one under the Palos Verdes peninsula, exhibiting primarily vertical displacements in the form of uplift.

Detailed recent three-dimensional modeling of the Palos Verdes fault zone (Wolfe et al., 2022) indicates that the fault has multiple segments and bends, but three main geographic and structural segments can be defined. These include the Santa Monica Bay, San Pedro Bay, and Lasuen Knoll segments. The Santa Monica Bay segment has been difficult to study because multiple, recurrent episodes of sea level drop during glacial periods in the Quaternary have exposed the sea floor, allowing for erosion to erase evidence of faulting in the sediments. However, the broad zone of diffuse seismicity in the bay indicates that the area is underlain by seismically active faults. Wolfe et al. (2022) studied a dense grid of marine seismic reflection data collected in the bay and determined, based on well-imaged offsets in the bedrock, that the Palos Verdes fault zone is comprised of multiple splays, with the main Palos Verdes fault strand consisting of a moderately southwest-dipping structure that includes several high-angle splays on its hanging wall. The fault zone bends northwesterly as it approaches the offshore Anacapa-Dume-Santa Monica fault system and appears to be truncated by it. Displacement on the Palos Verdes fault appears to decrease

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northward, but slip also seems to be transferred onto the Redondo Canyon fault zone. Several of these faults appear to have moved in the Holocene, and are therefore considered Holocene-active.

Slip rate on the Palos Verdes fault is poorly constrained at between 1.1 and 5.9 mm/yr. These are moderate to high rates of slip compared to other faults in the southern California region, and suggest that earthquakes on this fault occur about every 600 to 1,000 years (Wolfe et al., 2022). It is unknown when the Palos Verdes fault last ruptured in an earthquake. Based on the length of individual fault segments and the complexities of the fault zone, Wolfe et al. (2022) calculated that if a single segment of the Palos Verdes fault ruptures, the resulting earthquake would range between magnitude (Mw) 7.0 and 7.4, with the Santa Monica Bay segment likely causing a Mw 7.0 to 7.1 earthquake. However, if several segments rupture together, similar to the 1992 Landers earthquake, the resulting earthquake would range between Mw 7.4 and 7.8. Earthquakes this large would pose a significant hazard to the Los Angeles region, causing considerable damage and loss of life. Moreover, given that the Palos Verdes fault extends across both the ports of Los Angeles and Long Beach, and is located near the Los Angeles airport (LAX), rupture of this fault would have a significant impact on the economy of southern California. Rupture of the offshore sections could also result in local tsunamis that could impact these ports and other nearby coastal areas. The USGS has modeled a magnitude 7.7 earthquake on the Palos Verdes fault; the ShakeMap for that earthquake scenario indicates that PGAs in Santa Monica would range between about 0.2g and

0.75+g, with MMIs locally exceeding level VIII. Rupture of the offshore section of the fault could result in a significant tsunami in the Santa Monica area (see Section 7).

Newport-Inglewood Fault Zone
The onshore northwest-trending Newport-Inglewood fault zone (NIFZ) is discontinuous at the surface, consisting of a series of primarily left-stepping en echelon fault strands, each up to 4 miles (6.5 km) long, that extend from near Beverly Hills south to Newport Beach, a distance of approximately 41 miles (65 km). At Newport Beach, the fault continues offshore where it lines up with the deeply incised Newport Submarine Canyon (Fischer and Mills, 1991), and is comprised of five strands and three stepovers (Sahakian et al., 2017). Farther south and back onshore, the fault continues as the Rose Canyon fault, extending in a southeasterly direction through San Diego and the international border to Baja California, where it continues as the Agua Blanca fault. Overall, from Beverly Hills to Baja California, the fault zone is more than 185 miles (300 km) long (Grant and Rockwell, 2002).

The NIFZ is for the most part a right-lateral strike-slip fault. Vertical movement on this fault can occur and is inferred locally, the result of either a change in strike, or steps between the en echelons sections, with areas between left steps experiencing uplift, and areas between right steps experiencing extension and subsidence. Thus, the onshore section of the fault zone that extends through western Los Angeles and Orange counties is marked by a series of uplifts (anticlines) and low-lying areas typically occupied by salt marshes or estuaries. The uplifts include, from northwest to southeast, the Baldwin Hills, Rosecrans Hills, Dominguez Hills, Signal Hill and Reservoir Hill, Alamitos Heights and Landing Hill, Bolsa Chica Mesa, Huntington Mesa, and Newport Mesa (Barrows, 1974). These uplifts are petroleum traps that have been drilled and pumped successfully since the beginning of the 20th century. Several studies have identified multiple strands of the onshore segment of the NIFZ that have displaced Holocene-age terraces and sediments, showing that this fault is Holocene-active (Barrows, 1974; Shlemon et al., 1995; Grant et al., 1997).

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Figure 6-6: ShakeMap for a Magnitude 7.2 Earthquake Scenario on the Newport-Inglewood Fault Source: https://earthquake.usgs.gov/scenarios/eventpage/sclegacynewportinglewoodalt1m7p2_se/executive The slip rate for the Rose Canyon-NIFZ is poorly constrained at between 0.3 to 3.5 mm/yr (Woodward-Clyde Consultants, 1979; Fischer and Mills, 1991; Freeman, 1992; Lindvall and Rockwell, 1995; Grant et al., 1997). Fischer and Mills (1991) estimated an earthquake recurrence interval of between 200 and 800 years for the offshore segment of the NIFZ between San Mateo Point and Newport Beach. Paleoseismic studies by Shlemon et al. (1995) and Grant et al. (1997) suggest that the onshore segment of the NIFZ has had three to five ground rupturing earthquakes in the last 11,700±700 years. More recently, a study in the Seal Beach area (Leeper et al., 2017) uncovered evidence for several late Holocene subsidence events that the authors suggest are associated with earthquakes on the NIFZ. These researchers found evidence for three subsidence events in the past about 2,000 years, with the most recent event (MRE) occurring about 350 to 650 years ago. The recurrence interval between these burial events is, on average, approximately 700 years. A similar earthquake history and recurrence interval between earthquake events has been recently documented on the Rose Canyon fault from a trenching site in Old Town, San Diego (Singleton et al., 2019). The similarity between earthquake records has led these researchers to suggest that these faults rupture in sequence, with earthquakes on the Rose Canyon fault triggering ruptures on the NIFZ.

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The last significant earthquake on the NIFZ was the magnitude 6.3 Long Beach earthquake that occurred in 1933. This earthquake did not break the ground surface, but it caused significant damage to the region and caused an estimated 120 deaths. An earthquake of magnitude 7.2 on the onshore segment of the NIFZ has the potential to generate ground motions with PGAs of between

0.2g and 0.75+
g in the Santa Monica area, with the higher accelerations likely if the fault ruptures from south to north. MMIs in the city as a result of this earthquake scenario are estimated at between VII and VIII+
. The ShakeMap for this earthquake scenario is presented above, on Figure 6-6.

Compton Thrust Fault
The Compton Thrust fault is an inferred blind thrust fault in the southwestern portion of the Los Angeles basin. Because the fault does not extend upward to the ground surface, its location, extent, and even geometry are inferred. At least two different interpretations of the Compton Thrust fault have been proposed.

The first is based on high-resolution seismic reflection profiles of the Los Angeles basin that Shaw and Suppe (1996) analyzed to model the Compton fault as a ~25-mile- (~40-km-) long, northeastdipping low-angle blind thrust ramp that bends at two locations deep in the subsurface: 1) where the ramp meets the Central Basin decollement, a nearly flat fault surface that underlies the Los Angeles basin at a depth of about 6 miles (10 km), and 2) where the thrust ramp flattens at a depth of about 3 miles (5 km) just east of the Palos Verdes Hills and extends offshore into the Santa Monica Bay. In this model, when the thrust ramp moves during an earthquake, the sediments above these two locations are deformed. The northeastern zone of deformation is referred to as the Compton-Los Alamitos trend, whereas the southwestern zone is referred to as the Compton buried thrust or the Torrance-Wilmington-Belmont trend. Sorlien et al. (2004) have suggested that the San Pedro Escarpment and the Shelf Projection Anticlinorium, the structure thought responsible for the 1979 and 1989 earthquakes offshore Malibu, in the Santa Monica Bay, may be the updip projections of the Compton thrust ramp. Shaw and Suppe (1996) estimated a slip rate on this fault of 1.4 ± 0.4 mm/yr. This is the model used by the USGS in the ShakeMap magnitude 7.5 earthquake scenario presented in Figure 6-7. This earthquake scenario has the potential to cause severe to violent shaking in the Los Angeles region, including in the city of Santa Monica.

The second interpretation is that the Compton fault is a relatively high-angle, west-dipping, reverse oblique structure that bounds the eastern edge of the anticlines associated with the NewportInglewood fault. This interpretation is based on micro-seismicity (Hauksson, 1987), steep dips in the sedimentary units penetrated by oil exploratory wells (Wright, 1991; Yeats and Verdugo, 2010), and uplift to the east of the mapped traces of the NIFZ during the 1933 Long Beach earthquake (Barrows, 1974). Yeats and Verdugo (2010) used deep oil well records to look for evidence of repeated stratigraphic layers that would indicate faulting rather than folding. Their analysis found that strata at depth are faulted, with vertical separation across the fault measuring “hundreds of meters.” Combined, the data strongly suggest that the NIFZ and Compton-Los Alamitos faults are related, with strain partitioning occurring such that the NIFZ accommodates primarily strike-slip displacement while the Compton-Los Alamitos accommodates reverse movement. Yeats and Verdugo (2010) suggest, however, that the Compton-Los Alamitos is capable of producing earthquakes on its own. An earthquake scenario based on this fault interpretation is not available, but ground shaking in the region as a result of this earthquake is likely to be about the same or less than that presented in Table 6-3 and Figure 6-7.

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Figure 6-7: ShakeMap for a Magnitude 7.5 Earthquake Scenario on the Compton Thrust Fault The black rectangle with black lines shows the approximate location and extent of the Compton Thrust fault underneath the western edge of the Los Angeles basin. The fault is defined by a very low angle plane that is located several kilometers below the ground surface. Because of its shape and regional extent, this fault would cause strong ground shaking over a broad area if it causes an earthquake.

Source: https://earthquake.usgs.gov/scenarios/eventpage/bssc2014comptonellbgeol_m7p45_se/shakemap/intensity Puente Hills Thrust Fault
The ML 5.9 Whittier Narrows earthquake of October 1, 1987 first alerted geologists to the presence of seismically active blind thrust faults underneath the Los Angeles basin. Researchers like Davis et al. (1989), Shaw and Suppe (1996), and Shaw and Shearer (1999) began using oil field data to construct cross-sections through the area and interpret the sub-surface geology. Shaw and Shearer (1999) and Shaw et al. (2002) relocated the main shock and aftershocks of the 1987 earthquake, and showed that the earthquake sequence occurred on a section of a west- to northwest-trending

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buried thrust they called the Puente Hills blind thrust fault. Although the fault is blind, it is expressed at the surface by a series of low hills, including the Puente Hills on its eastern end.

Based on further work, these researchers divided the thrust fault into three segments referred to as the Los Angeles, Santa Fe Springs and Coyote Hills segments. The Santa Fe Springs segment is considered responsible for the 1987 earthquake. Dolan et al. (2003) and Leon et al. (2007) conducted subsurface studies using boreholes of the sediments folded above the Santa Fe Springs segment, and suggested that this fault has experienced at least four large (Mw 7.2 to 7.5) earthquakes in the past 11,000 years. Leon et al. (2007) also calculated a minimum Holocene rate of slip on this fault of between 0.9 and 1.6 mm/yr. Based on these data, UCERF3 (Field et al., 2013) assigned the Puente Hills thrust fault a preferred slip rate estimate of 0.9 mm/yr, and upper and lower slip rate bounds of 1.5 and 0 .2 mm/yr, respectively.

Figure 6-8: Scenario for a M7.1 Earthquake on the Puente Hills Fault Showing Estimated Intensity Values in the Region Resulting from this Event The black polygon shows the approximate location and extent of this buried thrust fault in the subsurface, underneath the north-central portion of the Los Angeles basin.

Source: http://earthquake.usgs.gov/earthquakes/shakemap/sc/shake/Puente_Hills_se/

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The Los Angeles segment of the Puente Hills thrust fault, the segment closest to Santa Monica, is estimated to be about 11 miles (18 km) long, with a dip of about 26 degrees to the northeast. If this segment ruptures by itself, it could generate a magnitude 6.7 to 7.0 earthquake. The M 7.1 ShakeMap earthquake scenario for the Puente Hills fault (see Figure 6-8 above), which is based on rupture of the Los Angeles segment, shows estimated PGAs in the Santa Monica area of between about 0.1g and 0.35+
g, with MMIs of between about VI and VII+. Stronger ground shaking would occur in the city, and in the region, if the Los Angeles segment of the Puente Hills thrust fault ruptures together with the Santa Fe Springs segment, or if the entire Puente Hills thrust fault ruptures together in one Mw 7.2 to 7.5 earthquake.

Field et al. (2005) conducted a loss-estimation analysis for different sized earthquakes on the Puente Hills thrust fault and found that an earthquake on this fault could be a worst-case scenario for the Los Angeles region, and possibly the costliest natural disaster in U.S. history. The scenarios suggest economic losses ranging between $82 and $252 billion (2005 dollars; approximately equivalent to $130.3 and $400.4 billion, respectively, in 2024), and between 3,000 and 18,000 fatalities. According to this study, some parts of Santa Monica could lose 10-25% of its building inventory (Figure 6-9).

Figure 6-9: Estimated Percent Building Loss as a Result of a Mw 7.5 Earthquake on the Puente Hills Thrust Fault
Source: Field and others, 2005, Loss Estimates for a Puente Hills Blind-Thrust Earthquake in Los Angeles, California: Earthquake Spectra, DOI: 10.1193/1.1898332.

Upper Elysian Park Thrust
The Elysian Park Fold and Thrust Belt (EPFT) was initially described by Davis et al. (1989), the first researchers to postulate that the Los Angeles area is underlain by a deep master detachment fault5F 6 and that most of the uplift in the region is caused by folding and blind thrust faulting at bends and kinks in the detachment fault. Subsequent work (cf., Bullard and Lettis, 1993; Shaw and Suppe, 1996; Shaw and Shearer, 1999; Oskin et al., 2000; Shaw et al., 2002) has highly modified the

6 A basal detachment fault, also referred to as a décollement (from French décoller 'to detach from'), is a horizontal to sub-horizontal gliding plane at the contact between two distinct rock masses that results in different styles of deformation in each block. In a compressional setting like the Los Angeles basin, the block above the detachment fault typically develops more intense deformation in the form of folding and faulting compared to the layer or block below.

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original model. The detachment fault at depth is now referred to as the Lower Elysian Park blind thrust, and a shallower reverse fault is called the Upper Elysian Park blind thrust. Both of these faults, like the Compton and Puente Hills thrusts, are “blind” because they are buried thousands of feet under the basin and are only expressed at the ground surface by the low hills that overlie them (such as the Elysian Park, Repetto, Montebello and Puente hills). The Lower Elysian Park blind thrust fault is the deepest, with its top about 6 miles (9.8 km) below the ground surface; the Puente Hills thrust is at a minimum about 3.1 miles (5 km) below the ground surface; and the Upper Elysian Park thrust is the shallowest, with the tip of the fault occurring about 1.9 miles (3 km) under the ground surface. The Lower Elysian Park thrust fault is interpreted to have a low seismic hazard, with a preferred slip rate of 0.01 mm/yr, and upper and lower bounds of 0.2 and 0 mm/yr respectively (UCERF3; Field et al., 2013). Given these values, this deep fault is typically no longer considered in seismic hazard assessments of the Los Angeles region. The Upper Elysian Park thrust fault, on the other hand, is considered a significant seismic source.

The length, location and slip rate of the Upper Elysian Park blind thrust were better defined by Oskin et al. (2000), who analyzed a series of small-scale folds on the south side of the Elysian Park hills (referred to as the Elysian Park anticline). These researchers modeled the fault as northeastdipping structure, and calculated a contraction rate in this part of the Los Angeles region that resolves into a slip rate of about 0.8 to 2.2 mm/yr on the Upper Elysian Park thrust fault. UCERF3 (Field et al., 2013) used the Oskin et al. (2000) values and assigned a best-estimate slip rate to this thrust fault of 1.9 mm/yr, with minimum and maximum rates of 0.8 and 2.2 mm/yr, respectively.

The approximately 12-mile- (20-km-) long fault is thought capable of producing Mw 6.2 to 6.7 earthquakes with a recurrence between earthquakes of 500 to 1,300 years. The USGS modeled a maximum credible earthquake of Mw 6.7 on the Upper Elysian Park thrust fault. The ShakeMap for that earthquake scenario, with the epicenter located north of downtown Los Angeles, estimates PGAs in the Santa Monica area of between about 0.1g and 0.35g, with MMIs of VI to VII+ .

Raymond Fault
The Raymond fault zone is about 15.5 miles (25 km) long and extends southwesterly from Monrovia, where it intersects the Sierra Madre fault at the foot of the San Gabriel Mountains, across the eastern and southern margins of Pasadena, to the northern reaches of Arcadia, San Marino and South Pasadena. A sharp gravity gradient and aerial photo lineaments suggest that the western end of the fault may connect to the eastern end of the Hollywood fault (Chapman and Chase, 1979; Crook et al., 1987; Dolan et al., 1995).

The fault is gently arcuate and convex to the south, and locally produces a very obvious southfacing scarp; the scarp is especially well defined near the middle of the fault trace (Crook et al., 1987; Weaver and Dolan, 2000). This led many geologists to originally favor reverse slip as the predominant sense of motion for the fault (Buwalda, 1940, as reported in Crook et al., 1987).

However, deflected channels, shutter ridges, sag ponds and pressure ridges along the fault’s main traces indicate that the Raymond fault is primarily a strike-slip fault (Jones et al., 1990). This sense of motion was substantiated by the seismological record, especially by the mainshock and aftershock sequence to the 1988 Pasadena earthquake of local magnitude (ML) 5.0 that occurred on this fault (Jones et al., 1990; Hauksson, 1994).

Several paleoseismic studies of the Raymond fault have been conducted, mostly across the North Branch of the fault. Crook et al. (1987) excavated a trench near Eaton Wash that exposed a 36- foot-wide fault zone that reportedly disturbed all sedimentary units to within about 1 foot of the surface, and they also investigated the fault at other locations. Dolan et al. (2000c) excavated more

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than 25 trenches in almost the same location as Crook et al.’s (1987) trench, while Weaver and Dolan (2000) conducted paleoseismic trenching of the Raymond fault in San Marino and at the Los Angeles Arboretum in Arcadia. Together these studies show that the most recent surface rupture on the western and central portions of the Raymond fault occurred between 1,000 and 2,000 years ago (Weaver and Dolan, 2000), and that between five and eight earthquakes occurred on this fault between 2,000 and 41,500 years ago. This yields a maximum average recurrence interval of between 5,700 and 10,000 years for earthquakes on the Raymond fault (Crook et al., 1987; Weaver and Dolan, 2000). Weaver and Dolan (2000) calculated a shorter recurrence interval of ~ 3,300 years for events between 41,500 and 31,500 years ago, based on evidence for three to five events during this time period. All of these earthquakes may be the result of clustering of activity on the Raymond fault during that 10,000-year period (not an unusual occurrence based on studies of other faults, such as the San Andreas), or it could be that the fault has caused several other earthquakes in the more recent past that were not well expressed in the trenches studied, and are therefore missing in the paleoseismic record. Dolan et al.’s study yielded a minimum late Holocene slip rate for the Raymond fault of ~ 4 +1/-0.5 mm/yr (Marin et al., 2000).

A conservative magnitude 6.9 earthquake on the Raymond fault would generate peak ground accelerations in the Santa Monica area of about 0.23g to 0.47g. The shaking would be perceived as very strong, and damage would be in the moderate to heavy ranges. However, the paleoseismic data suggest that this fault is capable of generating larger earthquakes, in the 7.0 magnitude range (Dolan et al., 2000b). If this is the case, stronger ground shaking as a result of an earthquake on this fault could be experienced in the Los Angeles region, including Santa Monica.

Verdugo Fault
The Verdugo fault is an approximately 13-mile- (21-km-) long, northwest-striking fault that extends along the northeastern edge of the San Fernando Valley, at or near the southern flank of the Verdugo Mountains. The fault dips to the northeast at between 55 and 80 degrees (Marshall et al., 2022). The Verdugo fault was first identified from scarps, offset alluvial deposits and differences in groundwater levels (Weber et al., 1980). Subsequent researchers relied on oil-well records and geophysical data to infer the fault’s subsurface characteristics (Tsutsumi and Yeats, 1999; Langenheim et al., 2000; Pujol et al., 2001). Vertical separation on the Verdugo fault is at least 0.6 mi (1 km) based, in part, on the structural relief between the valley floor and the crest of the Verdugo Mountains (Tsutsumi and Yeats, 1999), but the fault is also thought to have a left-lateral component of motion (Walls et al., 1998). Slip rate on the Verdugo fault is poorly constrained.

UCERF3 (Field et al., 2013) assigned it a preferred, geologically derived slip rate of 0.39 mm/yr, with a range between 0.12 and 0.99 mm/yr. The fault’s recurrence interval is unknown; however, the fault’s southern segment is thought to have ruptured during the Holocene, and the fault is therefore considered Holocene-active (Jennings, 1994). Based on its length, the Verdugo fault is thought capable of generating magnitude 6.0 to 6.9 earthquakes. A maximum magnitude 6.9 earthquake on this fault would generate peak ground accelerations in the Santa Monica area of about 0.1g to 0.2g, with MMIs in the VI to VII range.

Sierra Madre Fault
The Sierra Madre fault zone is a north-dipping reverse fault zone approximately 47 miles (75 km) long that extends along the southern flank of the San Gabriel Mountains from San Fernando to San Antonio Canyon, where it continues southeastward as the Cucamonga fault. The Sierra Madre fault has been divided into five segments, each with a different rate of activity.

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The northwestern-most segment of the Sierra Madre fault (the San Fernando segment) ruptured in 1971, causing the Mw 6.7 San Fernando (or Sylmar) earthquake. As a result of this earthquake, the Sierra Madre fault has been known to be active. In the 1980s, Crook et al. (1987) studied the Transverse Ranges using general geologic and geomorphic mapping, coupled with a few trenching locations. Based on this work, they suggested that segments of the Sierra Madre fault east of the San Fernando segment have not generated major earthquakes in several thousands of years, and possibly as long as 11,000 years. By California’s definitions of active faulting, most of the Sierra Madre fault would therefore be classified as not Holocene-active. Then, in the late-1990s, Rubin et al. (1998) trenched a section of the Sierra Madre fault in Altadena and determined that this segment had ruptured at least twice in the last 15,000 years, causing magnitude 7.2 to 7.6 earthquakes. This suggests that the Los Angeles area is susceptible to infrequent, but large nearfield earthquakes on the Sierra Madre fault. Rubin et al.’s (1998) trenching data show that during the last earthquake, the ground at the surface was displaced along the fault as much as 13 feet (4 meters), and that total displacement in the last two events adds up to more than 34 feet (10.5 meters).

Although the fault apparently slips at a slow rate of between 0.5 and 1 mm/yr (Walls et al., 1998), over time, it can accumulate a significant amount of strain. This relatively slow slip rate was also measured by Burgette et al. (2020) along the central Sierra Madre fault, where they infer an average slip rate of 1.1 +1.1/-0.4 mm/yr based on offset terrace and fan surfaces. The paleoseismic data obtained at the Altadena site (Rubin et al., 1998) were insufficient to estimate the recurrence interval and the age of the last surface-rupturing event on this segment of the fault. However, Tucker and Dolan (2001) trenched the east Sierra Madre fault at Horsethief Canyon and obtained data consistent with Rubin et al.’s (1998) findings. At Horsethief Canyon, the Sierra Madre fault last ruptured about 8,000 to 9,000 years ago. A recurrence interval of about 8,000 years was calculated using a slip rate of 0.6 mm/yr and a slip per event of 15 feet (5 meters). Therefore, if the last event occurred more than 8,000 years ago, it is possible that these segments of the Sierra Madre fault are near the end of their cycle, and are likely to generate an earthquake in the not-toodistant future.

The deterministic analysis for the Santa Monica area estimates peak ground accelerations of about

0.1g to 0.2g, based on a magnitude 7.2 earthquake on the central segment of the Sierra Madre fault. A larger earthquake on this fault, up to magnitude 7.6, would generate significantly stronger peak ground accelerations in the region, including in the Santa Monica area.

San Andreas Fault Zone
The San Andreas fault is the principal boundary between the Pacific and North American plates, and as such, it is considered the “Master Fault” because it has frequent (geologically speaking), large earthquakes, and it controls the seismic hazard in southern California. The fault extends nearly 800 miles (1,300 kilometers), from near Cape Mendocino in northern California to the Salton Sea region in southern California. Many refer to an earthquake on the San Andreas fault as “The Big One,” and for many parts of southern California, this is indeed true. Although, as shown in Table 6-3, several other faults closer to Santa Monica have the potential to cause stronger ground shaking, and therefore more local damage than the San Andreas fault, an earthquake on the San Andreas fault would cause extensive economic damage to the region, with, for example, potential losses to utilities (water, gas, and sewer lines, and the aqueducts that bring water to the Los Angeles area), and damage to the interstate freeways that are used to transport goods in and out of the State). Thus, the San Andreas fault should be considered in all seismic hazard assessment studies in southern California given its high probability of causing an earthquake in the

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near future. In 2007-2008, a group of scientists referred as the 2007 Working Group on California Earthquake Probabilities (WGCEP, 2008) calculated that the southern San Andreas fault had a 59% probability of causing an earthquake of at least magnitude 6.7 in the next 30 years. That probability increases with each passing year without an earthquake.

Large faults, such as the San Andreas fault, are generally divided into segments in order to evaluate their future earthquake potential. The segments are generally defined at discontinuities along the fault that may affect the rupture length. Each segment is assumed to have a characteristic slip rate (rate of movement averaged over time), recurrence interval (time between moderate to large earthquakes), and displacement (amount of offset during an earthquake). While this methodology has some value in predicting earthquakes, historical records and studies of prehistoric earthquakes show that it is possible for more than one segment to rupture during a large quake or for ruptures to overlap into adjacent segments. In central and southern California, the San Andreas fault zone is divided into five segments named, from north to south, the Cholame, Carrizo, Mojave, San Bernardino Mountains, and Coachella Valley segments. At its closest approach, the Mojave Section of the San Andreas fault is approximately 41 miles (66 km) northeast of Santa Monica.

The last major earthquake on the southern portion of the San Andreas fault was the 1857 Fort Tejon (M 7.7-8) event, which ruptured the Cholame, Carrizo, Big Bend, and Mojave North and Mojave South sections of the fault. This is the largest earthquake reported in California. The 1857 surface rupture broke a 186-mile- (300-km-) long section of the fault, resulting in displacements of as much as 27 feet (9 meters) along the rupture zone. Rupture of these fault segments as a group, during a single earthquake, is thought to occur with a recurrence interval of between 104 and 296 years. Figure 6-11 shows the PGAs and seismic intensities that would be expected in the southern California area if a repeat of the 1857 earthquake occurred.

Figure 6-10: ShakeMap for a Magnitude 7.8 Earthquake Scenario on the San Andreas Fault (repeat of the 1857 Fort Tejon Earthquake) Source: http://earthquake.usgs.gov/eqcenter/shakemap/sc/shake/1857_se/

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In 2008, the USGS modeled a magnitude 7.8-8 earthquake on the southern section of the San Andreas fault to identify the physical, social and economic consequences of a major earthquake in southern California. Referred to as the “ShakeOut scenario,” the earthquake modeled starts in the Salton Sea area, with the fault rupturing northward for 200 miles, toward Lake Hughes. This section of the San Andreas fault is thought to be long overdue for an earthquake because the average interval between earthquakes is about 115 to 220 years, and it has been more than 330 years since it last ruptured. Figure 6-11 is the ShakeMap for this hypothetical magnitude 7.8 “Shakeout” earthquake scenario. Comparison with the ShakeMap for the repeat of the Fort Tejon earthquake shown on Figure 6-10 shows that the epicenter location and fault rupture directivity have a significant impact on the ground shaking experienced in the region. The ShakeMap on Figure 6-10 shows that the area in and around Santa Monica would experience strong to very strong shaking (Modified Mercalli Intensity VI-VII), whereas the ShakeOut scenario is anticipated to cause very strong to severe shaking (Modified Mercalli intensity of VII-VIII) of long duration, possibly lasting several minutes. The long-period seismic waves caused by the ShakeOut earthquake in the Los Angeles region are expected to damage high-rise structures preferentially, but moderate damage to shorter, older structures is also likely. Economic losses in the entire southern California region as a result of the ShakeOut scenario were estimated at $200 billion (in 2008 dollars), with about 1,800 fatalities (Jones et al., 2008). Rose et al. (2011) revisited the losses as a result of the ShakeOut scenario and calculated $113 billion in property damage and more than $100 billion in business interruption (in 2008 dollars). These values are approximately equivalent to $162.9 and $144.1 billion, respectively, in 2024 dollars.

Figure 6-11: ShakeMap for a Magnitude 7.8 Earthquake Scenario (Shakeout) on the Southern San Andreas Fault
Source: https://earthquake.usgs.gov/scenarios/eventpage/sclegacyshakeout2full_se/executive

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San Jacinto Fault Zone
The San Jacinto fault zone consists of a series of closely spaced faults that form the western margin of the San Jacinto Mountains. The zone extends from its junction with the San Andreas fault in San Bernardino, just north of Rialto, southeasterly toward the Brawley area, where it continues south of the international border as the Imperial fault. This fault zone has a high level of historical seismic activity, having generated at least ten moderate (M6-7) earthquakes between 1890 and 1986.

Movement on the San Jacinto fault is predominantly right-lateral strike-slip, similar to the San Andreas fault, although Brown (1990) suggested that vertical motion contributes up to 10% of the net slip.

The San Jacinto fault zone has been divided into seven segments. Each segment, in turn, consists of a series of subparallel faults. The segment of the San Jacinto fault closest to Santa Monica is the San Bernardino segment, which is approximately 63 miles (101 km) west-northwest of the city at its closest. Slip rates on the various segments of the San Jacinto fault are less well constrained than for the San Andreas fault, but the data available suggest right-lateral slip rates of 12±6 mm/yr for the northern segments of the fault (including the San Bernardino segment) and slip rates of 4±2 mm/yr for the southern segments (WGCEP, 1995; Field et al., 2013).

Petersen and Wesnousky (1994) compiled data from various studies to suggest a recurrence interval of between 150 and 300 years for large ground-rupturing earthquakes on the San Jacinto fault. Since then, several new studies have helped refine these estimates. The most relevant of these studies were conducted at Mystic Lake, a site at the southern end of the San Bernardino segment, on the Claremont fault. Here, researchers have interpreted 12 surface-rupturing earthquakes in the past about 2,000 years (Marliyani et al., 2013; Onderdonk et al., 2015), which resolves into an average recurrence rate for the Claremont fault of 164 -8/+31 years (Onderdonk et al., 2014). The data also indicate that the average recurrence rate for the last four earthquakes is shorter, between about 100 and 140 years (Onderdonk et al., 2015), with the most recent groundrupturing earthquake thought to have occurred between A.D. 1800 and 1850 (Onderdonk et al., 2013). Thus, based on these data, the northern section of the San Jacinto fault is thought to be near the end of its earthquake cycle, and likely to rupture again in the not-too-distant future.

A maximum credible earthquake of magnitude 6.7 on the San Bernardino segment of the San Jacinto fault has the potential to generate light to moderate ground motions in the Santa Monica area. If the San Bernardino segment of the San Jacinto fault ruptures together with the San Jacinto Valley, Anza, and Clark segments to the south in an estimated Mw 7.7 earthquake, PGAs in Santa Monica are expected to range between about 0.05g and 0.2g, with MMIs in the V to VI range.

Shaking as a result of such an earthquake could potentially last at least a minute, if not longer, posing a risk to high rises and infrastructure such as bridges and freeway overpasses. Similar large rupture scenarios are also likely if the San Jacinto fault functions as an “earthquake gate” at Cajon Pass and ruptures together with the Mojave section of the San Andreas fault to the north (Onderdonk et al., 2018).

Surface Fault Rupture
Definitions and Statutory Requirements
Primary fault rupture refers to fissuring and offset of the ground surface along a rupturing fault during an earthquake. Primary fault rupture is rarely confined to a simple line along the fault trace.

As the rupture reaches the ground surface, it commonly spreads out into complex fault patterns of

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secondary faulting and ground deformation, especially in areas underlain by unconsolidated to poorly consolidated sediments, such as those underlying most of Santa Monica. Primary ground rupture typically results in a relatively small percentage of the total damage in an earthquake, but straddling a rupturing fault can cause severe damage to structures.

Secondary fault rupture refers to ground surface displacements along faults other than the main traces of active regional faults. Most of these subsidiary faults are not deeply rooted in the Earth’s crust and are not capable of producing damaging earthquakes on their own; movement along these faults generally occurs in response to movement on a nearby regional fault. Secondary ground deformation includes fracturing, shattering, warping, tilting, uplift and/or subsidence.

Surface displacement and distortion associated with secondary faulting and deformation can be relatively minor or can be large enough to cause significant damage to structures. Triggered slip as a result of a regionally large earthquake can also occur in faults many miles away from the causative fault. For example, as a result of the April 4, 2010 Sierra El Mayor earthquake in Baja California, triggered slip was reported on fault zones 40 to 60 miles away.

Faults have formed over millions of years, usually in response to regional stresses. Shifts in these stress regimes do occur over millennia. As a result, some faults change in character. For example, millions of years ago, the now right-lateral strike-slip NIFZ used to be a normal fault. Some faults may be abandoned altogether, and previously not active faults may be reactivated. Consequently, the State of California, under the guidelines of the Alquist-Priolo Earthquake Fault Zoning Act (APEFZA) of 1972, and in accordance with the most recent language in Special Publication 42 (CGS, 2018a) classifies faults according to the following criteria:
■ Holocene-Active: faults showing proven displacement of the ground surface within the past 11,700 years (within the Holocene Epoch);
■ Pre-Holocene: faults that have not moved in the past 11,700 years; and ■ Age-undetermined faults: faults whose recency of movement has not been determined.

Within the framework of the APEFZA, these faults are considered Holocene-active until proved otherwise.

In the past, faults were generally described as active, potentially active and not active, but these terms are not defined in the APEFZA, and often caused confusion from a regulatory perspective. In California, these definitions apply to structures intended for human occupancy, including some residential structures, and commercial and industrial buildings. Different definitions of activity are used by other agencies or organizations depending on the type of facility being planned or developed. For example, longer periods of inactivity are typically required for dams or nuclear power plants. An important subset of active faults is those with historical earthquakes.

The underlying assumption in this classification system is that if a fault has not ruptured the ground surface in the past 11,700 years, it is not likely to be the source of a damaging earthquake in the future. In reality, however, many faults have been insufficiently studied to determine their hazard level. Case in point, some of the faults that ruptured in the 1992 Landers, 1999 Hector Mine, and 2019 Ridgecrest earthquakes were previously thought to be not active, as they appeared to have not moved in at least 11,700 years, or were not even recognized as faults. Moreover, although simple in theory, the evidence necessary to determine whether a fault has or has not moved during the past 11,700 years can be difficult to obtain.

Development constraints within active fault zones were implemented in 1972 with passage of the

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APEFZA. This law prohibits the construction of new habitable structures astride a Holocene-active fault and requires special geologic studies to locate, and evaluate whether a fault has ruptured the ground surface in the last 11,700 years (CGS, 2018a). Because it is difficult and costly to safely reduce the effects of surface fault rupture through building and foundation design, the preferred and State-mandated mitigation measure is to avoid Holocene-active faults by avoiding placement of structures meant for human habitation across the trace of a Holocene-active fault. This is typically accomplished by establishing a structural setback from the surface projection of the fault as exposed in a trench or inferred from a subsurface study using borings, cone penetration tests (CPTs), and/or geophysical methods.

Santa Monica Fault Zone
The only fault currently mapped as extending through the city of Santa Monica that poses a surface-fault rupture hazard is the Santa Monica fault zone. As previously mentioned, this fault zone is part of the series of east- to east-northeast-trending faults that form the northern boundary of the Los Angeles basin. Defining the near-surface location and character of the Santa Monica fault has been difficult, as discussed further in the following paragraphs, with various interpretations provided by different researchers. Thus, depending on the source referenced, the Santa Monica fault zone occurs at or near the mountain-front of the Santa Monica Mountains, out in or underneath the coastal plain, or connecting both areas (see Figure 6-12).

The presence of a fault along the southern margin of the Santa Monica Mountains was suggested as early as 1914, when McLaughlin and Waring described the Santa Monica fault as one of the structural features of the northern Los Angeles region (based on the summary in Olson, 2018).

Hoots and Kew (1931), in the first comprehensive geologic map of the northern portion of the Los Angeles basin and the southern face of the Santa Monica Mountains, identified two east-trending faults in the Pacific Palisades area north of Santa Monica and several short, discontinuous bedrock faults in the mountains. Hoots and Kew (1931), however, did not identify any faults through the city of Santa Monica proper. The southernmost of the two short faults that these geologists mapped in the Pacific Palisades area is the Potrero fault. This fault used to be exposed in the cliff faces where Potrero Canyon meets the Pacific Ocean. The exposures were photographed and mapped by Johnson (1932) as part of a geologic feasibility study for the Quelinda Estate, a now fully developed residential area in the western half of Pacific Palisades. Johnson and his colleagues extended the Potrero fault eastward at least 1 mile from the mouth of Potrero Canyon (and thus about 0.5 miles farther east than Hoots and Kew) based on their analysis of changes in stream gradient and breaks in slope of the terrace surfaces. McGill (1989) extended the Potrero Canyon fault farther eastward based on breaks in slope and surface mapping of terrace deposits.

The next detailed geologic map of the area was prepared by Castle in 1960, who did not map any faults through the city. Then in 1965, Yerkes and others published a seminal study on the geology of the Los Angeles basin where they describe the Santa Monica fault as a major reverse fault at the boundary between geomorphic and geologic provinces. In their maps they show the fault as approximately located and consisting of two parallel to subparallel strands in the Santa Monica region, with these strands converging into one strand to the east, in the Hollywood area. These authors relied on subsurface data collected from oil wells to infer the location of the fault and evaluate its impact on the geologic units at depth. Specifically, Yerkes and others (1965) indicated that the basement rocks are vertically offset about 7,500 feet by the fault, with decreasing separation of the geologic units as the fault approaches the ground surface. In the Beverly Hills area, they reported that the Santa Monica fault dips about 50 degrees to the north at depth, and

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that matching the core of the Elysian Hills anticline across the fault suggests left-lateral offset in addition to vertical movement.

Figure 6-12: Faults Mapped and Inferred Through, Near and Below Santa Monica

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More detailed studies of the faults along the southern base of the Santa Monica Mountains began in the late 1970s and have continued to this day. Hill et al. (1978, 1979) and Hill (1979) mapped discontinuous scarps in the Pacific Palisades area and in the alluvial fans at the base of the Santa Monica Mountains. They used these features, combined with leveling studies across the extensively developed areas of Los Angeles, to postulate the presence of at least two faults in the subsurface east of the 405 Freeway. Other than the Potrero Canyon fault in Pacific Palisades, however, these researchers did not map any faults across Santa Monica. Wright (1991) relied on oil well data to conclude that the faults of the Santa Monica fault system are for the most part buried “under extensive landslides along the north shore of Santa Monica Bay and by a thick alluvial apron farther east.” A well drilled for petroleum in 1960 about four miles west of Beverly Hills confirmed the existence of a major fault in the subsurface, but this information was not disclosed by Wright until 1991. In the Santa Monica area, Wright showed the Santa Monica fault consisting of potentially two fault strands, but his maps are too small to reliably transfer that information to a map like the one on Figure 6-12. Wright (1991) referred to the southern of these faults as the Santa Monica fault proper, and the second, more northerly trace as the Potrero Canyon fault. Other geologists that have used oil and/or groundwater data to infer the location of the Santa Monica fault include Lang and Dreessen (1975), Dolan and Sieh (1992), and Yeats (2001).

Other methods that have been used to identify or infer these fault traces include mapping of surface or near-surface exposures (Johnson, 1932, and McGill, 1989, as discussed above; Hill et al., 1979; Crook et al., 1983; Dolan et al., 2000b), differential leveling analyses that have documented regional uplift or subsidence along discrete zones (Hill et al., 1979; Chapman and Chase, 1979), geomorphic mapping of folds that are thought to be the near-surface expression of the fault (Castle, 1960; Dolan and Sieh, 1992; Dolan et al., 2000a,b), and geophysical imaging (Dolan and Pratt, 1997; Pratt et al., 1998; Catchings et al., 2001; 2008). Work conducted by Dolan et al. (1992, 1997, 2000a) that built on the earlier work by Crook et al. (1983, 1992) concluded that the Santa Monica fault zone is comprised of north-dipping, high-angle, left-lateral reverse faults expressed at the surface by stepping broad folds that stretch across the western Los Angeles and Santa Monica region. These folds and scarps are located approximately 1.25 to 2.5 miles south of the base of the Santa Monica Mountains, in the plain that is covered in Quaternaryaged alluvial fan deposits (see the mapped scarps and folds in yellow on Figure 6-12). The 1992 work by Dolan and Sieh was referred to extensively by Leighton and Associates (1995) in defining the Fault Hazard Management Zones that were presented in the City of Santa Monica 1995 Safety Element of the General Plan.

Geophysical studies by Pratt et al. (1998) and Catchings et al. (2001, 2008), in addition to the work by Tsutsumi et al. (2001), confirmed that the Santa Monica fault zone consists of two main north-dipping branches that merge at a depth of approximately 1.25 miles (2 km). The northern branch has been investigated at the Veteran’s Administration property (Crook et al., 1983, Dolan et al., 2000a), and at University High School (Crook et al., 1983; MACTEC, 2004a, 2004b, 2007), where a series of steeply dipping to sub-vertical faults that offset late Quaternary deposits were exposed in trenches or interpreted from closely spaced borings and CPTs. The dip and normal sense of movement on the faults exposed by Dolan et al. (2000a) and MACTEC (2004a) suggest that these are upper-plate features rather than the main fault zone. However, these studies were the first to suggest that the Santa Monica fault has ruptured in the Holocene and should therefore be considered Holocene-active. Furthermore, Dolan et al.’ (2000a) study in the grounds of the Veteran’s Administration property suggests that this fault has moved five, and possibly six, times in the past 50,000 years, with an average recurrence interval of between 7,000 and 8,000 years.

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These studies were followed in 2011 by a fault investigation report issued by the Los Angeles County Metropolitan Transportation Authority (Metro) for the Century City area east of the 405 Freeway (Parsons Brinckerhoff, 2011) that summarized their seismic study of the west side of Beverly Hills, in the area of the proposed metro line and subway station on Constellation Boulevard. The report and accompanying maps inferred a complex zone of northeast-trending faulting along Santa Monica Boulevard, and north- to northwest-trending faulting associated with the northward extension of the Newport-Inglewood fault. Both fault systems were inferred to be Holocene-active although no age dating of the faulted sediments was conducted.

Based on a review of vintage topographic maps and photographs, new LiDAR technology, and the work conducted by Dolan, Crook and others, as discussed above, the CGS began to review the Hollywood and Santa Monica faults to determine whether they should be zoned following the criteria of the APEFZA. The Hollywood fault was zoned in 2014, and the State issued new APEFZ maps for the Santa Monica and Beverly Hills region in early 2018 (CGS, 2018a, 2018b). The zones of required investigation mapped by the CGS through the city of Santa Monica are presented in Figure 6-13. These zones supersede the Fault Hazard Management Zones presented in the 1995 City of Santa Monica Safety Element.

The APEFZ map (Figure 6-13) shows six generally east-west striking fault traces extending across the northern approximately one-third of the city (the official APEFZ maps for both the Topanga and Beverly Hills quadrangles were issued on January 11, 2018). The mapped or inferred fault traces are shown by the dashed red lines. The yellow shading surrounding the red fault lines are the zones of required investigation. If a property located inside or partially inside one of these yellowshaded areas is to be developed or re-developed, the applicant first needs to retain a Californiaregistered geologist to conduct a fault investigation before the building permit is granted. These studies need to be conducted in accordance with the guidelines provided in Special Publication 42 (CGS, 2018a). The only exception to this requirement is if the proposed structure is a singlefamily residence two stories or less in height. The study needs to conclusively show that the footprint of the proposed structure(s), and a certain distance beyond the structure(s), is not underlain by Holocene-active faults.

To date, approximately two dozen fault studies have been conducted in Santa Monica to comply with this requirement (Michael Phipps, geological reviewer for the City of Santa Monica, personal communication, 2023), and several more have been conducted to the east, in the city of Los Angeles. A few of these investigations have inferred faults at depth, typically at least 35 feet below the ground surface, but these inferred faults are capped by unbroken sediments and soils that, based on their characteristics and geomorphic position, are interpreted to be Pleistocene in age.

Thus, to date, no study has yet to expose a Holocene-active fault in the city of Santa Monica.

Similar findings have been reported from studies along Santa Monica Boulevard in the city of Los Angeles. The only two fault traces that, based on the data available to date, appear to extend upward to, or near the ground surface, include the fault mapped across the campus of University High School, and the Potrero Canyon fault in the Pacific Palisades area and northeastern corner of the city. Holocene activity on these faults has not been conclusively demonstrated, and as such, until proved otherwise, are considered Holocene-active.

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Liquefaction and Related Ground Failure
Definitions
Liquefaction is a geologic process that causes various types of ground failure. Liquefaction typically occurs in loose, saturated sediments primarily of sandy composition, in the presence of ground accelerations over 0.2g (Borchardt and Kennedy, 1979; Tinsley and Fumal, 1985).

Moderate magnitude (M>5.5) earthquakes can trigger liquefaction (Sana, 2021). Earthquake shaking suddenly increases pressure in the water that fills the pores between soil grains, causing the soil to have a total or substantial loss of shear strength, and behave like a liquid or semiviscous substance. Liquefaction can cause structural distress or failure due to ground settlement, a loss of bearing capacity in the foundation soils, and the buoyant rise of buried structures such as underground storage tanks. The excess hydrostatic pressure generated by ground shaking can result in the formation of sand boils or mud spouts, and/or seepage of water through ground cracks.

The types of ground failure typically associated with liquefaction are explained below.

Lateral Spreading – Lateral displacement of surficial blocks of soil as the result of liquefaction in a subsurface layer is called lateral spreading. Even a very thin liquefied layer can act as a hazardous slip plane if it is continuous over a large enough area. Once liquefaction transforms the subsurface layer into a fluid-like mass, gravity plus inertial forces caused by the earthquake may move the mass downslope towards a cut slope or free face (such as a river channel or a canal). Lateral spreading most commonly occurs on gentle slopes that range between 0.3° and 3°, and can displace the ground surface by several meters to tens of meters. Such movement damages pipelines, utilities, bridges, roads, and other structures. During the 1906 San Francisco earthquake, lateral spreads with displacements of only a few feet damaged every major pipeline. Thus, liquefaction compromised San Francisco’s ability to fight the fires that caused about 85 percent of the damage (Tinsley et al., 1985).

Flow Failure – The most catastrophic mode of ground failure caused by liquefaction is flow failure.

Flow failure usually occurs on slopes greater than 3 degrees. Flows are principally liquefied soil or blocks of intact material riding on a liquefied subsurface. Displacements are often in the tens of meters, but in favorable circumstances, soils can be displaced for tens of miles, at velocities of tens of miles per hour. For example, the extensive damage to Seward and Valdez, Alaska, during the 1964 Great Alaskan earthquake was caused by submarine flow failures (Tinsley et al., 1985).

Ground Oscillation – When liquefaction occurs at depth but the slope is too gentle to permit lateral displacement, the soil blocks that are not liquefied may separate from one another and oscillate on the liquefied zone. The resulting ground oscillation may be accompanied by the opening and closing of fissures (cracks) and sand boils, potentially damaging structures and underground utilities (Tinsley et al., 1985).

Loss of Bearing Strength – When a soil liquefies, loss of bearing strength may occur beneath a structure, possibly causing the building to settle and tip. If the structure is buoyant, it may float upward. During the 1964 Niigata, Japan earthquake, buried septic tanks rose as much as 3 feet, and structures in the Kwangishicho apartment complex tilted as much as 60 degrees (Tinsley et al., 1985).

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Ground Lurching – Soft, saturated soils have been observed to move in a wave-like manner in response to intense seismic ground shaking, forming ridges or cracks on the ground surface. At present, the potential for ground lurching to occur in a given area can be predicted only generally.

Areas underlain by thick accumulation of colluvium and alluvium appear to be the most susceptible to ground lurching. Under strong ground motion conditions, lurching can be expected in loose, cohesionless soils, or in clay-rich soils with high moisture content. In some cases, the deformation remains after the shaking stops (Barrows et al., 1994).

Liquefaction Susceptibility In and Near Santa Monica
As indicated above, there are three general conditions that need to be met for liquefaction to occur. The first of these–strong ground shaking of relatively long duration–can be expected to occur in the Santa Monica area as a result of an earthquake on any of several active faults in the region. The second and third conditions–loose, unconsolidated, water-saturated sediments consisting primarily of silty sand and sand within about 50 feet of the ground surface occur in some areas in and near Santa Monica. These areas include the coastline, where young beach and eolian sand deposits are mapped, and the portions of the channels of Santa Monica and Rustic canyons north of Santa Monica that are underlain by young alluvial deposits. Other areas where groundwater within 30 feet of the ground surface have been reported historically include 1) along the southwestern limits of the city, extending northward from Marina del Rey to the city’s southern boundary across Marine Park and eastward to near the southwestern corner of the Santa Monica airport; 2) near the northeastern corner of the city, between Brentwood Country Club to the north and just south of Santa Monica Boulevard on the south; and 3) an area approximately between Olympic Boulevard to the north, Pearl Street to the south, Gateway Boulevard on the east, and the southeast projection of Franklin Street on the west. This third area extends into the east-central edge of the city. Areas that the CGS has mapped as potentially susceptible to liquefaction are shown in light blue on Figure 6-14. These maps are typically regional in extent, and may not capture all areas susceptible to this hazard, so sites are typically evaluated on a case-by-case basis when a proposed new development or redevelopment project triggers a geotechnical investigation.

It is unlikely that new residential or commercial development will occur in some of the potentially liquefiable areas such as along the coastline and in the bottom of stream channels. However, structures such as bridges, roadways, major utility lines, and park improvements that could occupy these areas would be vulnerable to damage from liquefaction if mitigation measures are not included in their design. Any construction planned in these areas should include liquefaction mitigation measures, weighing the factors of public safety, the impact to the environment, and the risk of economic loss. For instance, a parking lot at the beach may not warrant ground modification measures, especially if the mitigation measures would be destructive to the environment, but a bridge abutment for a busy roadway would.

Seismically Induced Slope Failure
Strong ground shaking can worsen existing unstable slopes, particularly if coupled with saturated ground conditions. Seismically induced landslides can overrun structures, people or property, sever utility lines, and block roads, thereby hindering rescue operations after an earthquake. Over 11,000 landslides were mapped shortly after the Northridge earthquake, all within a 45-mile radius of the epicenter, including along the coastal bluffs in Santa Monica (Harp and Jibson, 1995, 1996). Although numerous types of earthquake-induced landslides have been identified, the most widespread type generally consists of shallow failures involving surficial soils and the uppermost

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weathered bedrock in moderate to steep hillside terrain (these are also called disrupted soil slides).

Rock falls and rockslides on very steep slopes are also common. The 1989 Loma Prieta and Northridge earthquakes showed that reactivation of existing deep-seated landslides also occurs (Spittler et al., 1990; Barrows et al., 1995).

A combination of geologic conditions leads to landslide vulnerability. These include high seismic potential; rapid uplift and erosion resulting in steep slopes and deeply incised canyons; highly fractured and folded rock; and rock with inherently weak components, such as silt or clay layers.

The orientation of the slope with respect to the direction of the seismic waves (which can affect the shaking intensity) can also control the occurrence of landslides.

Groundwater conditions at the time of the earthquake play an important role in the development of seismically induced slope failures. For instance, the 1906 San Francisco earthquake occurred in April, after a winter of exceptionally heavy rainfall, and produced many large landslides and mudflows, some of which were responsible for several deaths. The 1987 Loma Prieta earthquake however, occurred in October during the third year of a drought, and slope failures were limited primarily to rock falls and reactivation of older landslides that was manifested as ground cracking in the scarp areas but with very little movement (Griggs et al., 1991).

Areas that the State Geologist identifies as susceptible to earthquake-induced slope failure are shown in red on Figure 6-14. Within or immediately adjacent to the city of Santa Monica these areas include the coastal bluffs on the northern half of the city, the northwest-facing slopes along Santa Monica Canyon, some of the steeper slopes along the Brentwood Knoll, slopes along the I10 freeway, the slope on the southwestern side of the Santa Monica airport, and slopes in the neighborhood north of Dewey Street. For additional information regarding slope instability refer to Section 9.

VULNERABILITY ASSESSMENT
The effects of earthquakes span a large area, and large earthquakes occurring in the southern California area can and will be felt throughout the region. Although it is not possible to prevent earthquakes from occurring, their destructive effects can be minimized by strengthening buildings and structures. This is because most loss of life and injuries associated with earthquakes are related to the collapse of hazardous human-made structures. At risk from earthquake damage are large stocks of older buildings, bridges, facilities that house hazardous materials, dams, critical facilities, and private properties and businesses. Earthquakes can also cause extensive damage to the sewer, water, and natural gas systems; petroleum pipelines; and communication towers. Failure of these systems can fuel fires following an earthquake, or limit the water resources available to fight fires, and can severely limit the availability of utilities for days, weeks, or even months following an earthquake. This in turn can result in substantial losses in business interruption and secondary but significant health effects.

Other earthquake hazards, such as surface fault rupture, liquefaction and earthquake-induced landslides, can be as devastating as ground shaking. These hazards, and the areas of the City that could be impacted as a result of surface fault rupture, liquefaction and earthquake-induced slope failure, were previously described in this section. The potential impact of a tsunami is described in Section 7.

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Vulnerable Structure Types
Damage to the building stock in the southern California region is expected to vary due to differences in construction and construction quality. Some common building types and their earthquake performance are discussed in the sub-sections below. However, it is important to know that buildings are often a combination of steel, concrete, reinforced masonry and wood, with different structural systems on different floors or different sections of the building. Because different materials and construction types often react differently to seismic shaking, the overall combination can result in structural damage. Combination types that are potentially hazardous include:
concrete frame buildings without special reinforcing, precast concrete and precast-composite buildings, steel frame or concrete frame buildings with unreinforced masonry walls, reinforced concrete wall buildings with no special detailing or reinforcement, large capacity buildings with long-span roof structures (such as theaters and auditoriums), large un-engineered wood-frame buildings, buildings with inadequately anchored exterior cladding and glazing, and buildings with poorly anchored parapets and appendages (FEMA, 1985).

The seismic performance of buildings is tested when exposed to strong earthquakes. Building codes have often been modified in response to lessons learned in previous earthquakes. Thus, the 1997 version of the building code and all later building codes, including the 2022 edition of the California Building Code now being used, was the result of observations of intense ground shaking at levels higher than expected at Northridge in 1994, and again one year later, in Kobe, Japan.

These earthquakes and the 1992 Landers earthquake also showed that the direction of fault rupture plays a significant role in the distribution of ground shaking. As a result of these observations, current building codes incorporate near-fault site factors, soil-site effects and directivity effects.

As a result of the damage observed following the Northridge earthquake, many communities have implemented seismic retrofit ordinances for certain types of construction that are now known to not perform well when shaken by strong earthquakes. The City of Santa Monica is a leader in this effort, with seismic retrofit ordinances that target unreinforced masonry buildings (URMs), softstories, tilt-up buildings, non-ductile concrete buildings that were built before 1977, and steelmoment frame buildings that were built before 1990. This is discussed further in the following subsections. Additional information on the City’s Seismic Retrofit Program can be obtained directly from the City’s Building and Safety Division.

Unreinforced Masonry Buildings
Unreinforced masonry buildings (URMs) are prone to earthquake failure due to inadequate anchorage of the masonry walls to the roof and floor diaphragms, lack of steel reinforcing, the limited strength and ductility of the building materials, and sometimes, poor construction workmanship. Furthermore, as these buildings age, the bricks and mortar tend to deteriorate, making the buildings even weaker. Recognition of this issue led the State Legislature to pass Senate Bill 547, addressing the identification and seismic upgrade of URMs.

As of June 2023, Santa Monica staff had identified 89 URMs in the city in need of a seismic retrofit pursuant to the City’s Seismic Retrofit Ordinance. Of the 89 URMs, 56 cases were closed as a result of Requests for Reconsiderations and 16 URMs had successfully completed the required retrofit work and were in compliance. Of the remaining non-compliant URMs, 17 had been forwarded to Code Enforcement. The due date for the retrofit of URM buildings in Santa Monica was August 2019.

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Soft-Story Buildings
Soft-story buildings have a story, generally the first floor, lacking adequate strength or toughness due to too few shear walls. Apartments above glass-fronted stores, and buildings perched atop parking garages are common examples of soft-story buildings. Collapse of a soft story and “pancaking” of the remaining stories killed 16 people at the Northridge Meadows apartments during the 1994 Northridge earthquake (EERI, 1995). There are many other cases of soft-story collapses in past earthquakes. In response, the State encourages the identification and mitigation of seismic hazards associated with these types of potentially hazardous buildings, and others such as pre-1971 concrete tilt-ups, mobile homes, and pre-1940 homes.

As part of the City’s Seismic Retrofit Program, 1,686 soft-story buildings in the city of Santa Monica were identified as in need of retrofit. Of these soft-story buildings, 495 cases were closed as a result of Requests for Reconsiderations and 560 have had permits issued for retrofit. The remaining (43%) have until September 2025-July 2026 to submit plans to the City and complete the required retrofit, with the range in due date dependent on the number of stories and number of units in the structure. This due date for soft-story building types reflects a two-year extension granted pursuant to supplements to the City’s local COVID emergency order and codified on January 25, 2022, by Ordinance No. 2689 (CCS).

Wood-Frame Structures
Most wood-frame structures in Santa Monica can be anticipated to experience slight to extensive damage as a result of ground shaking expected in the region, the level of damage generally associated with the age of the structure, its condition, and its location relative to the causative fault, among other conditions. Structural damage to wood-frame structures often results from an inadequate connection between the superstructure and the foundation. These buildings may slide off their foundations, with consequent damage to plumbing and electrical connections.

Unreinforced masonry chimneys may also collapse. These types of damage are generally not life threatening, although they may be costly to repair. Wood frame buildings with stud walls generally perform well during an earthquake, unless they have no foundation or have a weak foundation constructed of unreinforced masonry or poorly reinforced concrete. In these cases, damage is generally limited to cracking of the stucco, which dissipates much of the earthquake's induced energy. The collapse of wood frame structures, if it happens, generally does not generate heavy debris, but rather, the wood and plaster debris can be cut or broken into smaller pieces by handheld equipment and removed by hand in order to reach victims (FEMA, 1985). These types of structures are currently not part of the City’s seismic retrofit program.

Pre-Cast Concrete Structures
Partial or total collapse of buildings where the floors, walls and roofs fail as large intact units, such as large pre-cast concrete panels, cause the greatest loss of life and difficulty in victim rescue and extrication (FEMA, 1985). In southern California, many of the parking structures that failed during the Northridge earthquake, such as the Cal-State Northridge and City of Glendale Civic Center parking structures, consisted of pre-cast concrete components (EERI, 1995).

Collapse of this type of structure generates heavy debris, and removal of this debris requires the use of heavy mechanical equipment. Consequently, the location and extrication of victims trapped under the rubble is generally a slow and dangerous process. Extrication of trapped victims within the first 24 hours after the earthquake becomes critical for survival. In most instances, however, post-earthquake planning fails to quickly procure equipment needed to move heavy debris. The

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establishment of Heavy Urban Search and Rescue teams, as recommended by FEMA (1985), has improved victim extrication and survivability. Buildings that are more likely to fail and generate heavy debris need to be identified, so that appropriate mitigation and planning procedures are defined prior to an earthquake.

Reinforced Masonry Tilt-up Buildings
Tilt-up buildings have concrete wall panels, often cast on the ground, or fabricated off-site and trucked in, which are then tilted upward into their final position. Connections and anchors have pulled out of walls during earthquakes, causing the floors or roofs to collapse. A high rate of failure was observed for this type of construction in the 1971 San Fernando and 1987 Whittier Narrows earthquakes. Tilt-up buildings can also generate heavy debris. This type of construction is often seen in commercial and industrial “box” type buildings like strip malls because it is fairly quick and economical way to build a structure.

The City’s Seismic Retrofit Program identified 42 tilt-up buildings in Santa Monica in need of a seismic retrofit pursuant to the City’s Seismic Retrofit Ordinance. As of June 2023, 5 cases were closed as a result of Requests for Reconsiderations, 17 had been retrofitted in compliance with the requirements of the Seismic Retrofit Ordinance, and 22 had been forwarded to Code Enforcement where compliance cases had been opened. The remaining properties were seeking compliance either through an active building permit or demolition application, or are City-owned and under consideration for pursuing a path to completing retrofit. Specifically, one project was in plan review, four projects permits were in ‘Issued’ status, and seven tilt-up buildings were City-owned.

The City-owned properties were pending review of a structural analysis with a preliminary determination that further analysis was required for three buildings located at Memorial Park, two buildings at Reed Park, and a commercial building (Bank of America) at 1301 4th Street. No further structural analysis was recommended for one City-owned building at Virginia Park. The due date for the retrofit of tilt-up buildings was August 2020.

Reinforced Concrete-Frame Buildings
Reinforced concrete frame buildings, with or without reinforced infill walls, display low ductility and are thus also referred to as non-ductile concrete (NDC) buildings. Earthquakes may cause shear failure (due to large tie spacings in columns, or have insufficient shear strength), column failure (due to inadequate rebar splices, inadequate reinforcing of beam-column joints, or insufficient tie anchorage), hinge deformation (due to lack of continuous beam reinforcement), and non-structural damage (due to the relatively low stiffness of the frame). A common type of failure observed following the Northridge earthquake was confined column collapse (EERI, 1995), where infilling between columns confined the length of the columns that could move laterally in the earthquake. These types of buildings are common not only in southern California, but abroad.

Casualties as a result of the “pancake-style” collapse of these structures in past earthquakes, including Mexico (1985), Armenia (1988), Nicaragua (1972), El Salvador (1986 and 2001), the Philippines (1990), Turkey (1999), China (2008) and most recently, in Turkey and Syria (2023), add to hundreds of thousands, with millions of people displaced from their homes in these types of structures.

Santa Monica’s Seismic Retrofit Program Update, dated March 8, 2022, indicated that 66 NDC buildings constructed prior to 1977 were identified in the city as requiring a seismic retrofit in compliance with the City’s Seismic Retrofit Ordinance. Of these, 32 have been closed as a result of Requests for Reconsiderations and 3 have been retrofitted in compliance with the requirements

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of the Seismic Retrofit Ordinance. Plans for retrofit have been submitted to the City for three NDC buildings, and 17 have had their cases sent to Code Enforcement. The City’s expected retrofit completion due date for NDC buildings is October 2027.

Multi-Story Steel-Frame Buildings
Multi-story steel frame buildings generally have concrete floor slabs. However, these buildings are less likely to collapse than concrete structures. Common damage to these types of buildings is generally non-structural, including collapsed exterior curtain wall (cladding), and damage to interior partitions and equipment. Overall, modern steel frame buildings have been expected to perform well in earthquakes, but the 1994 Northridge earthquake broke many welds in these buildings, a previously unanticipated problem.

Older, pre-1945 steel frame structures may have unreinforced masonry such as bricks, clay tiles and terra cotta tiles as cladding or infilling. Cladding in newer buildings may be glass, infill panels or pre-cast panels that may fail and generate a band of debris around the building exterior (with considerable threat to pedestrians in the streets below). Structural damage may occur if the structural members are subject to plastic deformation, which can cause permanent displacements.

If some walls fail while others remain intact, torsion or soft-story problems may result.

Another category of steel frame structures is referred to as welded steel moment frame buildings (SMF). These are structures where the connections between the steel framing members were welded together (as opposed to bolted together). The welded connections lack ductility and when subjected to seismic shaking, are likely to be stressed and deformed, resulting in structural damage. Welding instead of bolting was accepted by building codes and standards in the 1950s and into the 1990s. Many steel moment-resisting frame structures experienced unexpected brittle damage to their beam-to-column connections as a result of the 1994 Northridge earthquake, prompting a change to the building code standards.

The City of Santa Monica requires the seismic retrofit of all SMF structures built prior to January 1996. The City has identified 80 such structures in Santa Monica as requiring a seismic retrofit in compliance with the City’s Seismic Retrofit Ordinance. As of June 2023, of the 80 SMFs, 11 were closed, and 2 retrofits had been completed in compliance with the requirements of the City’s Seismic Retrofit Ordinance. The plan submittal due date for SMFs is October 2029, with a retrofit completion due date of October 2037.

Mobile Homes
Mobile homes are prefabricated housing units that are placed on isolated piers, jackstands, or masonry block foundations (usually without any positive anchorage). Floors and roofs of mobile homes are usually of plywood, and outside surfaces are covered with sheet metal. Mobile homes typically do not perform well in earthquakes. Severe damage occurs when they fall off their supports, severing utility lines and piercing the floor with their jackstands. Loss estimation analyses typically show that a large percentage of the mobile homes in the southern California area are likely to experience more than moderate damage as a result of an earthquake on a local fault.

Often, when manufactured homes fall off their supports, gas line connections are often severed.

The resultant gas leaks can ignite, which can lead to the complete loss of the structure due to fire.

This happened more recently in several older mobile homes in Ridgecrest following the July 4 and July 5, 2019 earthquakes in the area (Maison and Martinez, 2020).

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There is only one mobile home park in the city of Santa Monica (Mountain View Mobile Home Park at 1930 Stewart Street) with approximately 70 residences, and this mobile home park is currently not in the City’s seismic retrofit program.

Other Conditions that Can Lead to Structural Failure
In addition to building types, there are other factors associated with the design and construction of the buildings that also have an impact on the structures’ vulnerability to strong ground shaking.

Two of these conditions are discussed below:

Building Shape
A building’s vertical and/or horizontal shape can be important. Simple, symmetric buildings generally perform better than non-symmetric buildings. During an earthquake, non-symmetric buildings tend to twist as well as shake. Wings on a building tend to act independently during an earthquake, resulting in differential movements and cracking. The geometry of the lateral loadresisting systems also matters. For example, buildings with one or two walls made mostly of glass, while the remaining walls are made of concrete or brick, are at risk. Asymmetry in the placement of bracing systems that provide a building with earthquake resistance, can result in twisting or differential motions.

Pounding
Site-related seismic hazards may include the potential for neighboring buildings to "pound," or for one building to collapse onto a neighbor. Pounding occurs when there is little clearance between adjacent buildings, and the buildings "pound" against each other as they deflect during an earthquake. The effects of pounding can be especially damaging if the floors of the buildings are at different elevations, so that, for example, the floor of one building hits a supporting column of the other. Damage to a supporting column can result in partial or total building collapse.

Critical Facilities and Infrastructure
Earthquake damage to the region’s critical facilities and infrastructure needs to be considered and planned for. Critical (or essential) facilities are those parts of a community's infrastructure that must remain operational after an earthquake. Critical facilities include hospitals, fire and police stations, emergency operation centers, communication centers, and schools. These structures can be subclassified into the following groups based on their every-day function, and the risk that they pose to the community should they fail.
• High-risk facilities (also referred to as high potential loss facilities) are those that if severely damaged, may result in a disaster far beyond the facilities themselves. Examples include power plants, dams and flood control structures, freeway interchanges, bridges, and industrial plants that use or store explosives, toxic materials or petroleum products. • High-occupancy facilities have the potential to result in a large number of casualties or crowdcontrol problems. This category includes high-rise buildings, large assembly facilities, and large multi-family residential complexes.
• Dependent-care facilities, such as preschools and schools, rehabilitation centers, prisons, group care homes, nursing homes, animal shelters, and other facilities that house populations with special evacuation considerations.

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• Economic facilities are those that should remain operational to avoid severe economic impacts, such as banks, archiving and vital record-keeping facilities, airports, and large industrial or commercial centers.
• Lifelines (also referred to as utility and transportation systems) are those services that are critical to the health, safety and functioning of the community. They are particularly essential for emergency response and recovery after an earthquake. Lifeline systems include water, sewage, electrical power, communication, transportation (highways, bridges, railroads, and airports), natural gas, and liquid fuel systems. Critical facilities that remain functional during and immediately following an earthquake may not be able to provide the functions that they are designed for if the lifelines that they depend on are disrupted.

It is crucial that critical facilities have no structural weaknesses that can lead to collapse. For example, seismic performance goals for health care facilities typically include the following:
• The damage to the facilities should be limited to what might be reasonably expected after a destructive earthquake and should be repairable and not be life-threatening. • Patients, visitors, and medical, nursing, technical and support staff within and immediately outside the facility should be protected during an earthquake. • Emergency utility systems in the facility should remain operational after an earthquake. • Occupants should be able to evacuate the facility safely after an earthquake. • Rescue and emergency workers should be able to enter the facility immediately after an earthquake and should encounter only minimum interference related to out-of-place nonstructural components. • The facility should be available for its planned disaster response role after an earthquake.

The improved performance of critical structures and lifelines in the 1994 Northridge earthquake relative to the 1971 San Fernando earthquake, shows that the seismic codes upgraded and implemented after 1971 were effective. Nevertheless, the impact of the Northridge quake on lifeline systems was widespread and illustrates the continued need to study earthquake impacts, upgrade substandard elements in the systems, provide redundancy in systems, improve emergency response plans, and provide adequate planning, budgeting and financing for seismic safety.

Some of the observations and lessons learned from the Northridge earthquake are summarized below (from Savage, 1995; Lund, 1996). These observations have led to improvements and redundancies that will hopefully reduce the impact of future earthquakes. Nevertheless, all lifeline providers should prioritize the evaluation, upgrade and maintenance of their systems, with an emphasis on seismic strengthening.
• Several electrical transmission towers were damaged or totally collapsed. Collapse was generally due to foundation distress in towers that were located near ridge tops where amplification of ground motion may have occurred. One collapse was the result of a seismically induced slope failure at the base of the tower. • Damage to above ground water tanks typically occurred where piping and joints were rigidly connected to the tank, due to differential movement between the tank and the piping. Older steel tanks not seismically designed under current standards buckled at the

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bottom (called “elephant’s foot”), in the shell, and on the roof. Modern steel and concrete tanks generally performed well.
• The most vulnerable components of pipeline distribution systems were older threaded joints, cast iron valves, cast iron pipes with rigid joints, and older steel pipes weakened by corrosion. In the case of broken water lines, the loss of fire suppression water forced fire departments to utilize water from swimming pools and tanker trucks. • Significant damage occurred in water treatment plants due to sloshing in large water basins.
• A number of facilities did not have an emergency power supply or did not have enough power supply capacity to provide their essential services. • Lifelines within critical structures, such as hospitals and fire stations, were found to be vulnerable. For instance, rooftop mechanical and electrical equipment is not generally designed for seismic forces. During the Northridge quake, rooftop equipment failed causing malfunctions in other systems.
• A 70-year-old crude oil pipeline leaked from a cracked weld, spreading oil for 12 miles down the Santa Clara River.
• A freight train carrying sulfuric acid was derailed causing an 8,000-gallon acid spill and a 2,000-gallon diesel spill from the locomotive.

RISK ANALYSIS
Risk analysis is the third phase of a hazard assessment. Risk analysis involves estimating the damage and costs likely to be experienced in a geographic area over a period of time. Factors that can be considered in assessing earthquake risk include population and property distribution in the hazard area; the frequency of earthquake events; surface fault rupture, liquefaction and landslide susceptibility; type, age and number of buildings and infrastructure elements; and disaster preparedness of the region. This type of analysis can generate estimates of the damages to the region due to an earthquake event in a specific location. FEMA's software program HazUS uses mathematical formulas and information about building stock, local geology and the location and size of potential earthquakes, economic data, and other information to estimate losses from a potential earthquake. HazUS loss estimations were conducted for the City of Santa Monica as part of this study in September and October 2023 using Version 6.0 of the software. This methodology, including its benefits and limitations, is discussed further in the following sub-section.

HazUS
HazUS (which stands for Hazard US) is a standardized methodology for earthquake loss estimation based on a geographic information system (GIS). The methodology is a project of the National Institute of Building Sciences and is funded by the Federal Emergency Management Agency (FEMA). The HazUS project developed guidelines and procedures to make standardized earthquake loss estimates at a regional scale. With standardization, estimates can be compared from region to region. HazUS is designed for use by state, regional and local governments in planning for earthquake loss mitigation, emergency preparedness, response and recovery. HazUS addresses nearly all aspects of the built environment, and many different types of losses. The methodology has been tested by comparing scenario results with actual losses generated by several past earthquakes.

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The loss estimates include physical damage to buildings of different construction and occupancy types, damage to essential facilities and lifelines, number of after-earthquake fires and damage due to fire, and the amount of debris that is expected. The model also estimates the direct economic and social losses, including casualties and fatalities for three different times of the day, the number of people left homeless and number of people that will require shelter, number of hospital beds anticipated to be available, and the economic losses due to damage to the places of businesses, loss of inventory, and business interruption.

Although the loss estimation products are extremely helpful in assessing and comparing losses across regions, or as a result of different hazards, which in turn helps to prioritize mitigation actions, the results must be used with discretion. Loss estimation analyzes casualties, damage and economic loss in great detail based on a series of empirically derived functions applied to datasets that have some inherent limitations.

Some of the basics, assumptions and limitations in the methodology include:
• The basic level of analysis relies on databases built into the HazUS software that are based on generalized building square footage and value, population characteristics, costs of building repair, and basic economic data. Although these databases are based on the best available scientific, engineering, census and economic knowledge, there are inherent uncertainties. For example, there is incomplete scientific knowledge concerning earthquakes and their effects on buildings and facilities, and the software relies on approximations and simplifications to generate the analyses. As a result, the loss estimates may have a significant level of uncertainty. More accurate results may be possible if the basic databases are replaced with user-provided datasets, but this requires an extensive, time- and resource-consuming effort.
• HazUS is driven by statistics, and thus is most accurate when applied to a region, or a class of buildings or facilities. It is least accurate when considering a particular site, building or facility. Census tracts are the smallest regional units considered, with results averaged across individual census tracts. Ground motion demand for the general building stock is averaged over each census tract.
• The results of the building damage estimates are used to calculate the estimated number of casualties, including fatalities; monetary losses, including both cost to repair the structures and business interruption losses; and societal impacts, such as shelter needs. • Casualty estimates are computed from the structural damage output and do not include casualties that might occur during or after the earthquake that are not related to building damage (such as heart attacks, for example).
• The total system performance of the transportation system is not computed. • The baseline inventory database in HazUS includes an estimate of the potable water distribution pipeline length aggregated at the Census tract level, with 80% of the pipelines assumed to be brittle, and 20% ductile. For the wastewater distribution system, 60% of the pipelines are assumed to be brittle, and the remaining 40% are assumed to be ductile. For the gas distribution system, 10% of the pipes are assumed to be brittle; the rest are assumed to be ductile. For all of these systems, the methodology assumes that damage due to seismic waves will result in 80% leaks and 20% breaks, and that damage due to ground failure will result in 20% leaks and 80% breaks.
• The methodology does not consider the impact that failure of one lifeline system may have on another (cascading effects).

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• The methodology does not conduct a detailed system performance of the utility system. • Functionality estimates are based solely on damage to the buildings/structures and do not take emergency response or contingency plans into consideration. Thus, a hospital may be able to continue functioning by re-purposing their parking lots into treatment areas, but the software does not take that into consideration. Functionality estimates also do not consider damage to utilities or cascading effects.
• Shelter requirements are based on income of the displaced households, with 62% of the displaced households making less than $10,000 a year assumed to need shelter, and up to 13% of the displaced households making more than $40,000 per year assumed to need shelter. Given California’s high cost of living, use of these national income values for the HazUS scenarios likely underestimate the number of households that would seek shelter following an earthquake on a local fault.
• Loss of power and water are not considered in the estimates of short-term shelter needs.

The model also does not account for shelter needs in response to after-earthquake fire, dam failure inundation, or releases of hazardous materials. • The model does not consider the long-term impacts of housing damage on shelter needs.

The HazUS methodology produces seemingly precise numbers that can be easily misinterpreted.

Loss estimation's results, for example, may cite 454 left homeless by a scenario earthquake. This is best interpreted by its magnitude. That is, an event that leaves 400 people homeless is clearly more manageable than an event causing 4,000 or 40,000 homeless people; and an event that leaves 400,000 homeless would overwhelm the state’s resources. However, another loss estimation that predicts 600 people homeless should probably be considered equivalent to the 454 result. Because HazUS results make use of a great number of parameters and data of varying accuracy and completeness, it is not possible to assign quantitative error bars. Although the numbers should not be taken at face value, they are not rounded or edited because detailed evaluation of individual components of the disaster can help mitigation agencies ensure that they have considered all important options.

HazUS breaks critical facilities into two groups: essential facilities and high potential loss (HPL) facilities. Essential facilities provide services to the community and should be functional after an earthquake. Essential facilities include hospitals, schools, fire stations, police stations and emergency operations facilities. The essential facility module in HazUS determines the expected loss of functionality for these facilities. The damage probabilities for essential facilities are determined on a site-specific basis (i.e., at each facility). Economic losses associated with these facilities are computed as part of the analysis of the general building stock. Data required for the analysis include occupancy classes (current building use) and building structural type, or a combination of essential facilities building type, design level and construction quality factor. High potential loss facilities include dams, levees, military installations, nuclear power plants and significant hazardous material sites.

HazUS divides the lifeline inventory into two systems: 1) transportation and 2) utility lifelines. The transportation system includes seven components: highways, railways, light rail, bus, ports, ferry and airports. The utility lifelines include potable water, wastewater, natural gas, crude and refined oil, electric power and communications. If site-specific lifeline utility data are not provided for these analyses, HazUS performs a statistical calculation based on the population served.

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General Building Stock Type and Classification: HazUS provides damage data for buildings based on these structural types:
• Concrete
• Mobile (manufactured) home
• Precast concrete
• Reinforced-masonry bearing walls
• Steel
• Unreinforced-masonry bearing walls, and
• Wood frame
and based on these occupancy (usage) classifications:
• Residential (single-family and other residential)
• Commercial
• Industrial
• Agriculture
• Religion
• Government, and
• Education
As mentioned above, loss estimation for the general building stock is averaged for each census tract. Building damage classifications range from slight to complete. As an example, the building damage classification for light wood frame buildings is provided below. Wood-frame structures comprise the most numerous building type in Santa Monica.

Wood, Light Frame:
• Slight Structural Damage: Small plaster or gypsum-board cracks at corners of door and window openings and wall-ceiling intersections; small cracks in masonry chimneys and masonry veneer.
• Moderate Structural Damage: Large plaster or gypsum-board cracks at corners of door and window openings; small diagonal cracks across shear wall panels exhibited by small cracks in stucco and gypsum wall panels; large cracks in brick chimneys; toppling of tall masonry chimneys.
• Extensive Structural Damage: Large diagonal cracks across shear wall panels or large cracks at plywood joints; permanent lateral movement of floors and roof; toppling of most brick chimneys; cracks in foundations; splitting of wood sill plates and/or slippage of structure over foundations; partial collapse of "room-over-garage" or other "softstory" configurations; small foundations cracks. • Complete Structural Damage: Structure may have large permanent lateral displacement, may collapse, or be in imminent danger of collapse due to cripple wall failure or failure of the lateral load resisting system; some structures may slip and fall off the foundations; large foundation cracks.

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HazUS estimates two types of debris. The first is debris that falls in large pieces, such as steel members or reinforced concrete elements. These require special treatment to break into smaller pieces before they are hauled away. The second type of debris is smaller and more easily moved with bulldozers and other machinery and tools. This type includes brick, wood, glass, building contents and other materials.

Casualties are estimated based on the observation that there is a strong correlation between building damage (both structural and non-structural) and the number and severity of casualties. In smaller earthquakes, non-structural damage, (such as toppled bookshelves and broken windows) is typically responsible for most of the casualties. In severe earthquakes where there is a large number of collapses and partial collapses, there is a proportionately larger number of fatalities.

Data regarding earthquake-related injuries are, however, not of the best quality, nor are they available for all building types. Available data often have insufficient information about the type of structure in which the casualties occurred and the casualty-generating mechanism. HazUS casualty estimates are based on the injury classification scale described in Table 6-4.

Table 6-4: Injury Classification Scale
Injury Severity Level Injury Description
Severity 1 Injuries requiring basic medical aid without requiring hospitalization.

Severity 2
Injuries requiring a greater degree of medical care and hospitalization, but not expected to progress to a life-threatening status.

Severity 3
Injuries which pose an immediate life-threatening condition if not treated adequately and expeditiously. The majority of these injuries are the result of structural collapse and subsequent entrapment or impairment of the occupants.

Severity 4 Instantaneously killed or mortally injured.

The Severity 1 and Severity 2 casualties are most likely related to people running outside and, in the process, bumping into overturned furniture, walking barefoot on broken glass, and otherwise being hurt by non-structural elements, and by structural damage to residential structures and manufactured housing. Severity 3 and Severity 4 casualties are anticipated as a result of damage to residential structures other than single-family housing, and damage to commercial and industrial buildings.

In addition, HazUS produces casualty estimates for three times of day:
• Earthquake striking at 2:00 a.m. (most population at home) • Earthquake striking at 2:00 p.m. (most population at work/school) • Earthquake striking at 5:00 p.m. (commuting time)
Displaced Households/Shelter Requirements – Earthquakes can cause loss of function or habitability of buildings that contain housing. Displaced households may need alternative shortterm shelter provided by family, friends, temporary rentals, or public shelters established by the

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City, County or by relief organizations such as the American Red Cross. Long-term alternative housing may require import of mobile homes, occupancy of vacant units, net emigration from the impacted area, or, eventually, the repair or reconstruction of new public and private housing. The number of people seeking short-term public shelter is of most concern to emergency response organizations. The longer-term impacts on the housing stock are of great concern to local governments, such as cities and counties. As mentioned above, however, the software does not calculate the long-term shelter needs.

Economic Losses – HazUS estimates structural and nonstructural repair costs caused by building damage and the associated loss of building contents and business inventory. Building damage can cause additional losses by restricting the building's ability to function properly. Thus, business interruption and rental income losses are estimated. HazUS divides building losses into two categories: (1) direct building losses and (2) business interruption losses. Direct building losses are the estimated costs to repair or replace the damage caused to the building and its contents.

Business interruption losses are associated with inability to operate a business because of the damage sustained during the earthquake. Business interruption losses also include the temporary living expenses for those people displaced from their homes because of the earthquake. HazUS does not calculate business interruption losses due to failure of the lifeline systems (such as electric power outages).

Earthquakes may produce indirect economic losses in sectors that do not sustain direct damage.

All businesses are forward-linked (if they rely on regional customers to purchase their output) or backward-linked (if they rely on regional suppliers to provide their inputs) and are thus potentially vulnerable to interruptions in their operation. Note that indirect losses are not confined to immediate customers or suppliers of damaged enterprises. All of the successive rounds of customers of customers and suppliers of suppliers are affected. In this way, even limited physical earthquake damage causes a chain reaction, or ripple effect, that is transmitted throughout the regional economy.

HazUS Earthquake Scenarios for the Santa Monica Area
HazUS relies on census data, which are reported by geographical areas or tracts. The City of Santa Monica is defined by nineteen census tracts that combined match the city boundaries (see Figure 6-15). We used the population counts provided by the HazUS (version 6.0) 2020 database, which lists a population of 93,043 people in the 8.41 square mile area covered by the city. This number is slightly smaller (0.04% less) than the 2020 US Census figure of 93,076, and slightly larger (by

3.4%) than the American Communities 2022 population estimate for Santa Monica of 89,9476F7.

7 https://www.census.gov/quickfacts/fact/table/santamonicacitycalifornia/PST045222; accessed September 2023- March 2024.

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Figure 6-15: Census Tracts Used in the HazUS Analyses
(for a scaled, larger version of this map, refer to Plate H-6 in Appendix H) Four earthquake scenarios were modeled:
1) an earthquake on the Santa Monica fault that incorporates the Malibu fault to the west, and the Hollywood fault to the east, with the epicenter occurring in the Santa Monica Mountains, in the area of Universal City (see ShakeMap for this scenario on Figure 6-5) 2) an earthquake along the full-length of the Palos Verdes fault, from offshore Santa Monica southward to near the international border with Mexico. This scenario was used for a tsunami analysis (see Section 7), but the earthquake-related loss estimations are provided in this section, as a comparison with the other three earthquakes. 3) an earthquake on the onshore section of the Newport Inglewood fault, with the epicenter occurring near the southern end of the onshore section, in Orange County, and the fault unzipping northward (see ShakeMap for this scenario on Figure 6-6) 4) an earthquake on the southern San Andreas fault rupturing the southernmost section of the fault (the ShakeOut scenario prepared by the U.S. Geological Survey in the Fall of 2008 (Jones et al., 2008) (see the ShakeMap for this scenario on Figure 6-10) Specifics about each of these earthquake-producing faults were provided in the seismic sources section above, and in Table 6-5.

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Table 6-5: HazUS Earthquake Scenarios for the City of Santa Monica Fault Source Magnitude Description
Santa Monica 7.4
Low probability but high-risk earthquake event on a westtrending left-lateral oblique fault zone mapped through the northern portion of the city and extending eastward as the Hollywood fault, and westward as the Malibu fault. The fault can generate strong ground shaking and ground deformation in the form of surface fault rupture and folding in Santa Monica.

Palos Verdes 7.7
Medium probability, high-risk event on the fault that extends from the Santa Monica Bay in a southeastward direction
through the eastern edge of the Palos Verdes peninsula and then offshore to near the border with Mexico. Given the length of the fault, the earthquake would be large. Both strong ground shaking and a potential tsunami would impact the city of Santa Monica. This event would be devastating to the regional economy as it crosses both the Los Angeles and Long Beach ports.

NewportInglewood 7.2
Low to medium probability, medium to high-risk event on a northwest-trending right-lateral strike-slip event on the onshore Newport-Inglewood fault located near to, but outside City limits. This fault is considered to pose a significant hazard the Los Angeles basin.

Southern San
Andreas 7.8
High probability large earthquake that ruptures the entire southern San Andreas fault using the USGS ShakeOut scenario, with the epicenter near the Salton Sea, and the fault rupturing northward. Intense shaking of long duration is anticipated to rock the Los Angeles basin, with potentially devastating impacts to tall buildings and infrastructure, such as bridges. The impact to the region is expected to be substantial7F
8 .

Of the four earthquake scenarios modeled for the city, the results indicate that both a Mw 7.4 earthquake on the Santa Monica fault or a Mw 7.7 earthquake on the Palos Verdes fault have the potential to cause more damage in Santa Monica than a larger, but more distant earthquake on the San Andreas fault, or a not so-distant earthquake on the Newport-Inglewood fault. Specifics regarding the anticipated damage as a result of these four earthquake sources are summarized in the sub-sections below.

Building Damage
The HazUS database estimates that there are about 27,500 buildings in the city, with a total building replacement value (excluding contents) of nearly $19,682 million ($19,682,000,000).

Approximately 84% of the buildings considered in the analysis (and 69% of the building value, see Table 6-6) are associated with residential housing. In terms of building construction types found in the region, wood-frame construction makes up approximately 82% of the building inventory; the remaining 18% is distributed between the other general building types. Table 6-7 shows the estimated number of buildings by construction type anticipated to be damaged by the modeled

8 https://pubs.usgs.gov/of/2008/1150/

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earthquake scenarios.

Table 6-6: Building Exposure by Occupancy Type for the Study Area Occupancy Exposure
(in thousands of $) Percent of Total
Residential 13,512,940 68.7
Commercial 4,488,462 22.8
Industrial 672,168 3.4
Agricultural 7,255 0.0
Religion 200,401 1.0
Government 79,341 0.4
Education 721,343 3.7
19 681 910 Totals 19,681,910 100.0
Table 6-7: Number of Buildings* Damaged, by Construction Type * Based on an estimated total of about 27,500 buildings in the region.

Scenario Structure Type None Slight Moderate Extensive Complete Santa Monica Wood 7,808 9,527 4,470 463 142
Steel 102 145 347 313 144
Concrete 255 309 322 211 124
Precast 129 162 278 169 73
Reinforced Masonry 450 325 421 242 94
Unreinforced Masonry 47 71 116 82 77
Manufactured Housing 1 4 20 31 21
Totals 8,792 10,543 5,974 1,511 675
Palos Verdes
Wood 16,753 2,355 696 77 26
Steel 846 69 123 95 70
Concrete 923 98 105 59 20
Precast 658 48 86 87 47
Reinforced Masonry 2,689 289 436 357 105
Unreinforced Masonry 247 18 19 8 3
Manufactured Housing 78 1 2 1 0
Totals 22,194 2,878 1,467 684 271
Newport-Inglewood
Wood 14,401 6,464 1,457 71 17
Steel 499 233 237 70 12
Concrete 646 294 196 72 13
Precast 409 181 167 49 6
Reinforced Masonry 984 265 214 64 4
Unreinforced Masonry 185 101 77 24 6
Manufactured Housing 14 19 28 14 2
Totals 17,138 7,557 2,376 364 60
San Andreas
Wood 22,022 371 16 0 0
Steel 1,007 32 11 1 0
Concrete 1,186 30 6 0 0
Precast 778 24 9 1 0
Reinforced Masonry 1,496 25 9 1 0
Unreinforced Masonry 368 18 6 1 0
Manufactured Housing 68 6 3 0 0
Totals 26,925 506 60 4 0

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City of Santa Monica, California
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The HazUS models estimate that between about 570 and 18,703 buildings in Santa Monica will be at least slightly damaged in response to the earthquake scenarios modelled, with the lower number representative of damage as a result of an earthquake on the San Andreas fault, and the higher number representing damage as a result of an earthquake on the Santa Monica fault. These figures represent about 2 and 68 percent, respectively, of the total number of buildings considered in the analysis.

Similarly, the models estimate that between about 64 and 8,160 structures in Santa Monica will be at least moderately damaged by these earthquake scenarios. These figures represent about 0.2 and 30 percent, respectively, of the total number of buildings considered, with the lowest number representative of the damage as a result of the San Andreas fault earthquake scenario, and the higher number representing damage as a result of the Santa Monica fault earthquake scenario. The models also estimate that approximately 675 buildings in Santa Monica will be damaged beyond repair by an earthquake on the Santa Monica fault. That amounts to about 2 percent of the entire building stock in the city. The modeled Palos Verdes and Newport-Inglewood fault earthquakes are estimated to damage beyond repair about 236 and 60 buildings, respectively, in Santa Monica.

Given that wood-frame buildings comprise the most common construction type in Santa Monica, the largest number of buildings in the city damaged by the earthquake models are wood-frame structures. Specifically, the models indicate that approximately 14,602 wood-frame buildings in the city will be at least slightly damaged by a Santa Monica fault earthquake event. This amounts to 65 percent of the total number of wood-frame buildings in Santa Monica. The Palos Verdes and Newport-Inglewood earthquake scenarios return estimates of 2,743 and 8,009 wood-frame buildings, respectively, that are at least slightly damaged. These numbers amount to about 16 and 36 percent, respectively, of the total number of wood-frame buildings in the city. The San Andreas ShakeOut earthquake scenario is estimated to result in at least slight damage to about 386 woodframe structures, which amounts to about 2 percent of the more than 22,000 wood-frame structures present in the study area.

However, as a percentage of total number of buildings of each construction type, the models suggest that an earthquake on the Santa Monica fault will cause at least slight damage to nearly 99 percent of the manufactured houses in the city, and at least slight damage to 90 percent of the steel-frame buildings. Similarly, about 88, 84 and 79 percent of the unreinforced masonry, pre-cast and concrete structures, respectively, will be at least slightly damaged by that earthquake scenario.

Even the distant San Andreas ShakeOut scenario is anticipated to at least slightly damage about 12 percent of the manufactured homes stock, 6 percent of the unreinforced masonry buildings, and 4 percent of the steel and pre-cast concrete structures in Santa Monica. Based on these data, woodframe buildings are actually the safest building type in the city, consistent with observations made in many previous earthquakes that have found that wood-frame structures perform well during earthquakes8F
9 . Reasons for this include that wood-frame buildings are lightweight, ductile but strong, and structurally redundant (meaning that that the hundreds of structural elements and thousands of nail connections can and do compensate if adjacent members and joints fail). Woodframe structures in particular perform quite well in an earthquake caused by a distant fault because wood has the flexibility necessary to withstand the long-period waves associated with such an earthquake, unlike other less-ductile construction types. This in part also explains why the earthquake scenarios other than the San Andreas fault result in a lower percentage of damaged wood-frame structures.

9 https://cwc.ca/wp-content/uploads/publications-BP5_WoodFramesAndEarthquakes.pdf, accessed April 2, 2024.

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Packet Pg. 905 Attachment: 2025 SM LHMP Volume 2: Hazards [Revision 1] (7378 : Local Hazard Mitigation Plan Update) Local Hazard Mitigation Plan Section 6
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Table 6-8 below summarizes the modeled damage to buildings in Santa Monica by occupancy type based on the four earthquake scenarios considered.

Table 6-8: Number of Buildings* Damaged, by Occupancy Type Scenario Occupancy Type Slight Moderate Extensive Complete Total Santa Monica
Commercial 806 1,051 636 320 2,813
Education 21 19 9 4 53
Government 8 10 7 3 28
Industrial 105 161 105 58 429
Single-Family Residential 6,944 3,218 298 76 10,536
Other Residential 2,611 1,465 425 198 4,699
Agriculture 7 7 4 2 20
Religion 41 43 27 14 125
Total 10,543 5,974 1,511 675 18,703
Palos Verdes
Commercial 306 367 308 116 1,097
Education 7 6 4 1 18
Government 3 4 4 2 13
Industrial 45 63 63 28 199
Single-Family Residential 1,780 625 83 44 2,532
Other Residential 724 378 200 71 1,373
Agriculture 2 2 2 1 7
Religion 14 15 13 6 48
Total 2,881 1,460 677 269 5,287
Newport-Inglewood
Commercial 817 607 167 26 1,617
Education 17 10 3 0 30
Government 8 6 2 1 16
Industrial 119 105 34 6 264
Single-Family Residential 4,649 1,008 44 10 5,711
Other Residential 1,903 612 106 16 2,637
Agriculture 6 4 1 0 11
Religion 38 24 7 1 70
Total 7,557 2,376 364 60 10,356
San Andreas
Commercial 87 23 2 0 112
Education 1 0 0 0 1
Government 1 0 0 0 1
Industrial 16 6 1 0 23
Single-Family Residential 264 12 0 0 276
Other Residential 132 18 1 0 151
Agriculture 1 0 0 0 1
Religion 4 1 0 0 5
Total 506 60 4 0 570
* Based on a total of about 27,500 buildings in the region.

As a percentage of building damage by occupancy type, the models estimate that about 66 percent of the residential structures, including single-family homes and others (i.e., multi-family residential buildings, including duplexes, condominiums and apartments, and manufactured homes) will suffer at least slight damage as a result of a magnitude 7.4 earthquake on the Santa Monica fault; more than 24 percent will have at least moderate damage. Nearly 84 percent of the industrial structures and about 80 percent of the commercial structures in the city will be at least slightly

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damaged by an earthquake on the Santa Monica fault; 63 and 57 percent, respectively will suffer at least moderate damage. These figures indicate that an earthquake on the Santa Monica fault will pose a significant economic impact to the city and its residents.

The Palos Verdes fault earthquake scenario is estimated to result in at least slight damage to about 17 percent of the residential structures in the city, with about six percent experiencing moderate to complete damage. About 31 percent of the commercial structures and about 38 percent of the industrial structures are also expected to be at least slightly damaged by this earthquake event.

Twenty-three percent of the commercial structures and nearly 30 percent of the industrial structures in the city are estimated to experience moderate to complete damage as a result of large-magnitude earthquake on the Palos Verdes fault.

The Newport-Inglewood earthquake scenario is estimated to result in at least slight damage to about 36 percent of the residential structures in the city, with about 8 percent experiencing moderate to complete damage. About 46 percent of the commercial structures and 52 percent of the industrial structures are also expected to be at least slightly damaged by this earthquake event.

The models also suggest that 23 percent of the commercial structures and 28 percent of the industrial structures in the city will experience moderate to complete damage as a result of the Newport-Inglewood fault scenario.

The San Andreas ShakeOut scenario, on the other hand, is modeled to result in at least slight damage to less than 2 percent of the residential structures in the city, with about 3 percent of the commercial and nearly 4.5 percent of the industrial buildings modeled to be at least slightly damaged by a ShakeOut-type earthquake. These numbers drop to about 0.7 and 1.4 percent, respectively, for commercial and industrial structures experiencing moderate to extensive damage.

None of the structures in Santa Monica are expected to be completely damaged by this earthquake scenario.

The citywide distribution, by census tract, of the damage expected to residential structures in Santa Monica as a result of the four earthquake scenarios modeled using HazUS is shown on Figure 6-16. The percentages shown for each tract are calculated using the estimated total residential building loss (in dollars) divided by the total residential building exposure (in dollars). The maps show that the Santa Monica fault earthquake scenario would do more damage to the central and northern portions of the city closer to the Santa Monica fault, where both surface fault rupture and strong ground shaking would be expected. An earthquake on the offshore Palos Verdes fault is expected to cause most damage in the western portion of the city closest to that fault. An earthquake on the Newport-Inglewood fault, which is located to the southeast of Santa Monica, is expected to cause a higher percentage of damage to structures on the eastern and central portions of the city. The San Andreas fault is far enough from Santa Monica that damage as a result of that earthquake is approximately equal and relatively low throughout the city.

Figure 6-17 show the regional distribution of the damage to commercial structures as a percentage of total commercial building exposure by census tract. The regional impact to commercial structures by each earthquake scenario generally matches the regional distribution of damaged residential structures shown on Figure 6-16. Comparison of the two figures shows that the earthquake scenarios will do more damage to commercial structures than to residential buildings, consistent with the findings presented in the paragraphs above. Note that the same color scheme was used for both figures, with darker shades of a given color indicating a higher percentage of building damage.

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Figures 6-16 and 6-17 in particular show that a 7.4 magnitude earthquake on the Santa Monica fault is the worst-case earthquake scenario for the city of Santa Monica, with a relatively high percentage of damaged residential structures and a significantly higher percentage of damaged commercial structures. The Palos Verdes fault has the potential to cause substantial damage in the city too, followed by the Newport-Inglewood fault in terms of severity. Although not modeled for this study, an earthquake on the section of the Compton buried thrust fault that underlies the city may result in damage similar to that modeled from an earthquake on the Palos Verdes fault. The data presented here shows that the San Andreas fault earthquake scenario, although most likely, is anticipated to result in only minor damage in Santa Monica. This does not consider, however, the impacts that rupture of the San Andreas fault is expected have on the southern California region as a whole. For a description of the anticipated damage to southern California as a result of the ShakeOut scenario, the reader is encouraged to read the report by Jones et al. (20089F 10).

10 https://pubs.usgs.gov/publication/ofr20081150

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Packet Pg. 908 Attachment: 2025 SM LHMP Volume 2: Hazards [Revision 1] (7378 : Local Hazard Mitigation Plan Update) Local Hazard Mitigation Plan Section 6
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Figure 6-16: Total Residential Building Related Losses as a Percentage of Total Residential Building Exposure

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Packet Pg. 909 Attachment: 2025 SM LHMP Volume 2: Hazards [Revision 1] (7378 : Local Hazard Mitigation Plan Update) Local Hazard Mitigation Plan Section 6
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Figure 6-17: Total Commercial Building Related Losses as a Percentage of Total Commercial Building Exposure

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Total Economic Losses: Sum of Building-Related and Lifeline-Related Losses HazUS breaks down building-related losses into two categories: 1) direct building losses and 2) business interruption losses. Direct building losses (capital stock losses in Table 6-9) are the estimated costs to repair or replace the structural and non-structural damage caused to a building and its contents, and in the case of businesses, damage to inventory. Income losses, or businessinterruption losses, are related to the inability to operate a business because of the damage it sustained during the earthquake. Business interruption loss estimates also include the temporary living expenses for those people displaced from their homes because of the earthquake. Income losses, however, do not include losses related to the inability to operate the business because of lifeline outages or damage to the transportation network limiting access to a business.

Table 6-9 shows the building-related economic loss estimates (in $ millions) calculated by HazUS for each of the four earthquake scenarios considered for this study. The models estimate that total building-related losses in the city of Santa Monica will range from about $31 million for an earthquake on the San Andreas fault, to $3,414 million for an earthquake on the Santa Monica fault. Between 14 and 23 percent of these estimated losses are related to business interruption in the city, with loss in wages and relocation expenses amounting to about 60 percent of the total income losses. An earthquake on the Santa Monica fault is estimated to be at least 2.3 times costlier than the Palos Verdes fault earthquake scenario, and about 3.4 times costlier than an earthquake on the Newport-Inglewood fault.

As a function of dollar loss, damage to residential occupancies (single-family and other residential structures combined) accounts for between about 42 and 45 percent of the total building-related losses estimated for each earthquake scenario. The estimated losses for commercial occupancies also account for between 39 and 45 percent of the total building-related economic losses.

The total economic losses estimated for the city of Santa Monica include the building-related losses presented in Table 6-9, combined with the lifeline-related losses estimated for the area (presented in Table 6-10). The lifeline-related losses are the costs of repairing or replacing the damaged transportation and utility systems. The transportation system includes highways, railways, light rail, ferry facilities, port facilities, and the airport. The utility system includes potable and waste water, natural gas, oil systems, electrical power and communication. The losses to the transportation and lifeline systems do not include losses related to business interruption as a result of lifeline outages.

Based on the data presented in Table 6-10, an earthquake on the Santa Monica fault is anticipated to cause slight damage to the bridges and tunnels that are part of the highway system, with a loss ratio of about 6.25 percent of the inventory value. Combined damage to the light rail and airport facilities in the city is estimated to cost about $9.94 million; this amounts to a 32.6 percent loss ratio. Significantly, the airport runways are not damaged by this earthquake scenario. Economic losses related to the utility system are dominated by damage to the potable water and waste water distribution lines. Although the estimated losses to the electrical power system are shown as zero, other data provided by HazUS and discussed later in this report suggest that the electrical power system is damaged extensively by a Santa Monica fault earthquake scenario. The loss estimates to the transportation and lifeline systems as a result of other earthquake scenarios are only a small fraction of that estimated for the Santa Monica earthquake. Examining Santa Monica only, the HazUS results for the Newport-Inglewood fault scenario report no damage to the lifelines system; these results are suspect, however, with numbers similar to those generated by either the Palos Verdes or San Andreas earthquake scenarios considered more likely.

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City of Santa Monica, California
2025 Earthquakes Page 6-70
Table 6-9: Building-Related Economic Loss Estimates (in Million $) Area SingleFamily
Other
Residential Commercial Industrial Others Total
Santa Monica Fault Earthquake Scenario
Income
Losses
Wage 0.00 23.0956 146.1667 2.8905 6.3086 178.4614
Capital-Related 0.00 9.8164 135.3765 1.7034 2.1290 149.0253 Rental 8.2771 54.051 63.4010 1.4165 3.4982 130.6438
Relocation 30.8467 30.9302 96.2093 6.6907 29.4593 194.1362 Subtotal 39.1238 117.8932 441.1535 12.7011 41.3951 652.2667 Capital
Stock
Losses
Structural 66.9854 85.3777 182.4707 27.2748 26.4824 388.5910 Non-Structural 341.3432 548.1378 610.6316 95.1211 113.8058 1,709.0395 Content 107.6299 130.0402 271.5938 60.6893 54.3210 624.2742 Inventory 0.00 0.00 30.6030 8.9174 0.3749 39.8953
Subtotal 515.9585 763.5557 1,095.2991 192.0026 194.9841 2,761.80 Total 555.08 881.45 1,536.45 204.70 236.38 3,414.07
Newport-Inglewood Fault Earthquake Scenario
Income
Losses
Wage 0.00 4.5963 40.9619 0.8456 1.8698 48.2736
Capital-Related 0.00 1.9534 37.5366 0.5007 0.6259 40.6166 Rental 2.2646 13.6755 19.4119 0.4982 1.0025 36.8527
Relocation 7.9477 8.1903 28.8340 2.6097 8.3059 55.8876
Subtotal 10.2123 28.4155 126.7444 4.4542 11.8041 181.6305 Capital
Stock
Losses
Structural 21.0865 22.4195 46.1067 7.9588 6.7911 104.3626 Non-Structural 119.1254 169.2796 163.0665 27.5616 32.8862 511.9193 Content 40.1606 45.1788 81.0080 18.3410 18.9053 203.5937 Inventory 0.00 0.00 9.0198 2.6685 0.1231 11.8114
Subtotal 180.3725 236.8779 299.2010 56.5299 58.7057 831.6870 Total 190.58 265.29 425.95 60.98 70.51 1,013.32
Palos Verdes Fault Earthquake Scenario*
Income
Losses
Wage 0 16 64 1 77 158
Capital-Related 0 7 67 1 8 83
Rental 3 23 15 0 2 43
Relocation 10 13 23 1 7 54
Subtotal 13 59 169 3 94 338
Capital
Stock
Losses
Structural 28 40 44 4 10 126
Non-Structural 114 265 185 17 43 624
Content 47 97 170 20 39 373
Inventory 0 0 11 1 0 12
Subtotal 189 402 410 42 92 1,135
Total 202 461 579 45 186 1,473
San Andreas Fault Earthquake Scenario
Income
Losses
Wage 0.000 0.0703 0.9804 0.0237 0.0583 1.1327
Capital-Related 0.000 0.0298 0.9242 0.0140 0.0194 0.9874 Rental 0.0385 0.3332 0.6060 0.0183 0.0232 1.0192
Relocation 0.0845 0.1690 0.6860 0.0949 0.1690 1.2034
Subtotal 0.1230 0.6023 3.1966 0.1509 0.2699 4.3427
Capital
Stock
Losses
Structural 0.6458 0.6506 1.2045 0.2548 0.1660 2.9217
Non-Structural 3.6565 5.2220 5.7821 1.1030 1.2480 17.0116 Content 0.9811 1.2065 2.8418 0.6886 0.6849 6.4029
Inventory 0.000 0.000 0.3052 0.0993 0.0041 0.4086
Subtotal 5.28349 7.0791 10.1336 2.1457 2.1030 26.7448
Total 5.41 7.68 13.33 2.30 2.37 31.09
• The loss estimates for the Palos Verdes fault scenario were generated using the combined Tsunami and Earthquake HazUS module; the results provided were rounded to the closest whole integer.

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Table 6-10: Estimated Transportation and Utility System Economic Losses System
Components Inventory Value
(millions of
dollars)
Economic Loss (millions of dollars) Per Earthquake Scenario Transportation
Santa Monica
Fault
NewportInglewood FaultPalos Verdes
Fault
San Andreas
Fault
Highway 1,190.5 7.6831 1.8057 0.95 0.158
Railway 376 0 0 0 0
Light Rail 512 5.3539 3.4285 0 0.6613
Ferry 0 0 0 0 0
Port 7.62 0 1.3635 1.86 0.2419
Airport 24.76 4.5818 2.9553 0 0.5615
Sub-Total 2,110.60 17.62 9.55 2.80 1.48
Lifelines
Potable Water 7.7958 1.5901 0 0.23 0.3329
Waste Water 4.6775 0.7988 0 0.11 0.1672
Natural Gas 86.2719 0.2737 0 0.04 0.0573
Oil Systems 0 0 0 0 0
Electrical Power 0 0 0 0 0
Communication 0 0 0 0 0
Sub-Total 98.75 2.66 0 0.38 0.56
Total Building-Related Losses
(from Table 6-9) 3,414.07 1,013.22 1,473 31.09
Total Economic Losses 3,434.35 1,022.87 1,476.18 33.13
Casualties
Table 6-11 provides a summary of the casualties estimated for the earthquake scenarios on the Santa Monica, Palos Verdes, Newport-Inglewood and San Andreas faults. In all cases, the models indicate that the highest number of casualties are expected to occur as a result of an earthquake during the day, during maximum occupancy of commercial, industrial and educational facilities.

These numbers reflect the higher damage, as a percentage, to construction types other than woodframed, and to occupancy types other than residential, as described in the section above. More specifically, steel, concrete, precast, reinforced masonry and unreinforced masonry construction types are more often used for commercial, industrial, and educational purposes, and since these types of construction are expected to not perform well overall, the highest number of casualties are associated with the time of the day when these types of buildings are more likely to be occupied.

An earthquake on the Santa Monica fault occurring around 2 PM is estimated to result in more than 1,000 people being hurt enough to need medical treatment, although with no need for hospitalization (Level 1). The same earthquake scenario is estimated to result in approximately 275 people hurt with non-life-threatening injuries that do require hospital care (Level 2), and 44 people hurt with life-threatening injuries (Level 3). The number of injured people requiring hospitalization could overwhelm the local hospitals, assuming that when the earthquake occurs, 50 to 80 percent of the 531 total hospital beds available in the study area are already occupied by in-care patients.

Approximately 85 people in the city are estimated to die as a result of a Santa Monica fault earthquake in response to building damage alone. The next-most damaging earthquake in the city in terms of casualties is an event occurring during peak commute time, which HazUS models at 5 PM. The least number of casualties are attributed to an earthquake in the early morning hours (2 AM), when most people are at home.

Earthquakes on the Palos Verdes and Newport-Inglewood faults are estimated to result in similar numbers of casualties if only earthquake damage is considered (an earthquake on the offshore

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section of the Palos Verdes in Santa Monica Bay could generate a tsunami that could result in significant casualties along the coastline; tsunami-generated casualties are not included in Table 6-11). The earthquake models for the Newport-Inglewood and Palos Verdes faults estimate Level 1 casualties (lowest acuity) of about 167 to 186 people for a 2 PM event, with total estimated deaths of between 7 and 14 people. As with the Santa Monica earthquake scenario, the number of casualties is expected to be less if the earthquake strikes during maximum commuting time, and even less if it occurs at night, during maximum residential occupancy.

Given the low number of damaged structures anticipated as a result of an earthquake on the San Andreas fault, the total number of casualties resulting from building damage is low, regardless of the time of day when the San Andreas fault earthquake strikes. In all cases, casualties are estimated by HazUS as a result of only structural and non-structural damage to buildings. Thus, the estimated casualty numbers do not include injuries or deaths that might occur during or after the earthquake not related to building damage, such as “heart attacks, car accidents, mechanical failures due to power outages, incidents during post-earthquake search and rescue, postearthquake cleanup and construction, electrocution, tsunami, landslides, liquefaction, fault failure, dam failures, fires, or hazardous materials releases.”10F 11 It also does not account for injury or death
related to disruptions in access to prescription drugs or regular medical care, like dialysis.

Therefore, all of the numbers presented in Table 6-11 could be slightly higher to account for these other potential causes of injury or even death.

11 FEMA P-366, 2023, HazUS Estimated Annualized Earthquake Losses for the United States; available from https://www.fema.gov/sites/default/files/documents/fema_p-366-hazus-estimated-annualized-earthquake-lossesunited-states.pdf; accessed in March and April 2024.

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Packet Pg. 914 Attachment: 2025 SM LHMP Volume 2: Hazards [Revision 1] (7378 : Local Hazard Mitigation Plan Update) Local Hazard Mitigation Plan Section 6
City of Santa Monica, California
2025 Earthquakes Page 6-73
Table 6-11: Estimated Casualties*
1B
Earthquake Scenario Santa Monica Fault (M 7.4) Palos Verdes Fault (M 7.7) Time Sectors Level 1 Level 2 Level 3 Level 4 Level 1 Level 2 Level 3 Level 4 2 A.M.
(max.
residential
occupancy)
Commercial 11 3 1 1 2 1 0 0
Commuting 0 0 0 0 0 0 0 0
Educational 0 0 0 0 0 0 0 0
Hotels 1 0 0 0 0 0 0 0
Industrial 7 2 0 0 1 0 0 0
Other Residential 212 54 8 16 36 8 1 2
Single-Family 48 7 0 1 8 1 0 0
Total 279 66 9 18 48 10 1 3
2 P.M.
(max
educational,
industrial,
and
commercial)
Commercial 636 178 28 56 140 36 5 11
Commuting 0 0 0 0 0 0 0 0
Educational 231 63 10 20 22 6 1 2
Hotels 0 0 0 0 0 0 0
Industrial 50 14 2 8 2 0 1
Other Residential 69 18 3 5 13 3 0 1
Single-Family 16 2 0 0 3 0 0 0
Total 1,002 275 44 85 186 47 7 14
5 P.M.
(peak
commute
time)
Commercial 385 108 17 33 81 21 3 6
Commuting 2 2 4 1 0 0 1 0
Educational 72 19 3 6 1 0 0 0
Hotels 0 0 0 0 0 0 0 0
Industrial 31 9 2 3 5 1 0 0
Other Residential 82 21 3 6 14 3 0 1
Single-Family 19 3 0 0 3 0 0 0
Total 591 162 29 49 104 26 4 8
Time Sectors Newport-Inglewood Fault (M 7.4) San Andreas Fault (M 7.8 ShakeOut) 2 A.M.
(max.
residential
occupancy)
Commercial 2 1 0 0 0 0 0 0
Commuting 0 0 0 0 0 0 0 0
Educational 0 0 0 0 0 0 0 0
Hotels 0 0 0 0 0 0 0 0
Industrial 1 0 0 0 0 0 0 0
Other Residential 37 6 1 1 1 0 0 0
Single-Family 15 1 0 0 0 0 0 0
Total 55 8 1 1 1 0 0 0
2 P.M.
(max
educational,
industrial,
and
commercial)
Commercial 99 19 3 5 2 0 0 0
Commuting 0 0 0 0 0 0 0 0
Educational 43 8 1 2 1 0 0 0
Hotels 0 0 0 0 0 0 0 0
Industrial 8 2 0 0 0 0 0 0
Other Residential 12 2 0 0 0 0 0 0
Single-Family 5 0 0 0 0 0 0 0
Total 167 31 4 7 3 0 0 0
5 P.M.
(peak
commute
time)
Commercial 59 12 2 3 1 0 0 0
Commuting 0 0 1 0 0 0 0 0
Educational 15 3 0 1 0 0 0 0
Hotels 0 0 0 0 0 0 0 0
Industrial 5 1 0 0 0 0 0 0
Other Residential 14 2 0 0 1 0 0 0
Single-Family 6 0 0 0 0 0 0 0
Total 99 18 3 4 2 0 0 0
*Based on a 2020 estimated population of 93,043, with values rounded to whole numbers.

Level 1: Medical treatment without hospitalization Level 2: Hospitalization but not life threatening Level 3: Hospitalization and life threatening Level 4: Fatalities due to scenario event

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Damage to Critical and Essential Facilities
HazUS breaks critical facilities into two groups: (1) essential facilities, and (2) high potential loss (HPL) facilities. Essential facilities are those parts of a community's infrastructure that must remain operational after an earthquake, such as hospitals, emergency operation centers, fire and police stations, schools, and communication centers. HPL or high-risk facilities are those that if severely damaged, may result in a disaster far beyond the facilities themselves. Examples include power plants, dams and flood control structures, and industrial plants that use or store explosives, extremely hazardous materials or petroleum products in large quantities. No HPL facilities were modeled in Santa Monica proper, but damage to HLP facilities outside City limits could potentially impact section of Santa Monica and its residents. The impact that failure of Stone Canyon Dam would have on the eastern portion of the city is described in detail in Section 8.

The critical facilities that were considered in the earthquake scenarios for the Santa Monica area include 27 schools, two (2) emergency operations centers (the main EOC near City Hall, and a secondary EOC at the airport, two (2) hospitals, five (5) police stations and four (4) fire stations.

The EOC at the Main Library was not considered in the analysis. The expected damages to these essential facilities as a result of the earthquake scenarios conducted for this study are summarized in Table 6-12 below.

Table 6-12: Estimated Damage to Critical Facilities as a Result of the Earthquake Scenarios Earthquake
Scenario Facility Type Total Number
Number of Facilities
With at Least
Moderate
Damage >50%
With Complete
Damage >50%
With
Functionality
>50% on Day 1
Santa
Monica
Hospitals 2 1 0 0
Schools 27 16 0 5
EOCs 2 0 0 1
Police Stations 1 0 0 1
Fire Stations 5 2 0 0
Palos Verdes
Hospitals 2 0 0 2
Schools 27 2 0 25
EOCs 2 0 0 2
Police Stations 1 0 0 1
Fire Stations 5 1 0 4
NewportInglewood
Hospitals 2 0 0 2
Schools 27 1 0 18
EOCs 2 0 0 2
Police Stations 1 0 0 1
Fire Stations 5 0 0 5
San Andreas
Hospitals 2 0 0 2
Schools 27 0 0 27
EOCs 2 0 0 2
Police Stations 1 0 0 1
Fire Stations 5 0 0 5
The earthquake scenarios indicate that an earthquake on the San Andreas fault is not likely to cause damage to any of the critical and essential facilities in the study area, with all facilities expected to be more than 50 percent functional immediately after the earthquake. An earthquake on the Santa Monica fault, on the other hand, is likely to cause at least moderate damage to one of the hospitals, with neither hospital expected to be more than 50 percent functional on the first day

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after the earthquake. Two (2) of the fire stations are also expected to have at least moderate damage. Furthermore, on the first day after the earthquake, none of the fire stations is expected to be more than 50 percent functional. Although both EOCs are expected to perform fairly well, only one of the EOCs is expected to be more than 50 percent functional immediately after the earthquake. The HazUS model also estimates that about 16 of the 27 schools in the city will experience at least moderate damage, with only five (5) schools being more than 50 percent functional on the first day after the event.

Both hospitals and the two EOC locations are expected to be more than 50 percent functional following either the Palos Verdes or Newport-Inglewood earthquake scenario. The models also suggest that 25 of the 27 schools considered in the analyses will be more than 50 percent functional on the day after a Palos Verdes earthquake scenario; in the case of the NewportInglewood fault scenario, the estimate is 18 out of 27 schools. The models also suggest that at least one school will experience at least moderate damage in response to an earthquake on the Palos Verdes fault, whereas the Newport-Inglewood earthquake scenario is anticipated to result in at least moderate damage to one school and one of the fire stations.

Other critical facilities not considered in the HazUS analyses that should be considered in both emergency preparedness and emergency response operations given their potential impact on the community include: (1) High-occupancy facilities such as high-rise buildings, large assembly facilities, and large multi-family residential complexes because of the potential for a large number of casualties or crowd-control problems; (2) dependent care facilities such as preschools, rehabilitation centers, group care homes, nursing homes, and other facilities that house populations with special evacuation considerations; and (3) economic facilities such as banks, archiving and vital, record-keeping facilities, and large industrial or commercial centers that should remain operational to avoid severe economic impacts.

Utility Systems Damage
Damage to pipelines considers two states: leaks and breaks. Leaks generally occur in response to seismic wave propagation, and occur as a result of the joints separating, or crushing of the bell at the bell-spigot connection. Breaks typically occur in response to ground deformation, such as fault rupture, liquefaction, or landsliding. Breaks take a lot longer to fix than a leak, with a crew of four utility workers estimated to take four hours to fix a leak in a pipe 20 inches or less in diameter, and the same crew estimated to take eight hours to fix a break in the same pipe. Leaks in pipes more than 20 inches in diameter are estimated to take a four-person crew ten hours to fix, whereas a break is estimated to take the same crew 20 hours to fix. HazUS uses these estimates to calculate how many days it will take to repair the damaged pipes and restore service. The estimated number of breaks and leaks to the potable and waste water systems and the natural gas system as a result of three earthquake scenarios is summarized in Table 6-13 below.

According to the models, the Santa Monica fault earthquake scenario will result in more than 350 leaks in the potable water distribution lines and 88 breaks within Santa Monica city limits.

Similarly, the waste water system will experience about 178 leaks and 44 breaks. The Palos Verdes and San Andreas fault earthquake scenarios are expected to cause leaks and breaks to both the potable and waste water systems, although in lesser numbers than the Santa Monica earthquake scenario. Although not analyzed, the Newport-Inglewood fault scenario is expected to result in damage similar to that modeled for the Palos Verdes fault. Damage to the local pipelines as a result of the San Andreas fault earthquake scenario returned a relatively high number of leaks and

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breaks that are probably related to the long-period seismic waves anticipated in the Los Angeles basin region, including Santa Monica. All of these earthquakes will also result in leaks and breaks of the water mains and sewer lines throughout the wider geographic region. The San Andreas fault ShakeOut earthquake, in particular, is anticipated to cause significant damage to the southern California water distribution system, with broken pipes, damage to the aqueducts bringing water into the region, and impaired infrastructure. This in turn is expected to result in widespread disruptions to the water supply and other associated problems.

Table 6-13: Estimated Damage to Pipelines as a Result of Three Earthquake Scenarios System
Total
Length of
Pipelines
(km)
Santa Monica Fault Palos Verdes Fault San Andreas Fault # of Leaks # of Breaks # of Leaks # of Breaks # of Leaks # of Breaks Potable Water 390 353 88 51 13 74 18
Waste Water 234 178 44 25 6 37 9
Natural Gas 24 5 1 2 1 1 0
Oil Systems 0 0 0 0 0 0 0
It is noteworthy to mention that the HazUS inventory does not include any oil pipelines through the city, but that there is in fact one petroleum pipeline that extends in a northerly direction across the eastern portion of the city. This pipeline crosses the mapped traces of the Santa Monica fault, so if this fault breaks in an earthquake, rupture to that pipeline should be expected. This is discussed further in the section on hazardous materials.

The results of the analyses regarding the functionality of the potable water and electric power systems in the city for three of the earthquakes discussed herein are presented in Table 6-14. The HazUS inventory for the Santa Monica area does not include specifics regarding the various lifeline systems in the city, therefore, the models estimated damage to the potable water and electric power using empirical relationships based on the number of households served in the area, combined with, in the case of the water distribution system, the number of breaks and leaks anticipated in the system. The high number of leaks and breaks in the potable water system as a result of the Santa Monica earthquake scenario means that a large number of households (nearly 72 percent) will likely not have potable water one day after the earthquake. Repairing the damage is anticipated to take several days; as a result, even on the third day after the earthquake, nearly 5,000 households are expected to not have water in their faucets. Therefore, residents should be advised to have drinking water stored as part of their earthquake emergency kits. These drinking water reserves should be enough to provide 1 gallon of water for all members of the household (including pets) for at least 3 days, and preferably one week.

Although the models anticipate that both the Palos Verdes and San Andreas earthquake scenarios will not result in any households in the city being without potable water immediately after the earthquake, given that both leaks and breaks in this system are anticipated, it is appropriate to expect that some neighborhoods may be without potable water for a few days also. Thus, the recommendation to have enough drinking water stored in bottles to last at least a few days is appropriate.

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Table 6-14: Expected Performance of Potable Water and Electricity Services Scenario Utility Number of Households without Service*
Day 1 Day 3 Day 7 Day 30 Day 90
Santa Monica Potable Water 33,955 4,916 0 0 0
Electric Power 36,011 23,284 9,566 796 47
Palos Verdes Potable Water 0 0 0 0 0
Electric Power 3,866 1,958 554 24 6
San Andreas Potable Water 0 0 0 0 0
Electric Power 0 0 0 0 0
*Based on Total Number of Households = 47,422
The models also suggest that the Santa Monica earthquake scenario will cause considerable damage to the electric power system, with nearly 76 percent of Santa Monica households expected to be without electricity on the first day after the earthquake. Repair of the system is expected to take days to weeks, with nearly 10,000 households modeled to be without electricity one week after the earthquake, and nearly 50 households still without electricity three months out.

The Palos Verdes earthquake event is expected to cause approximately one-tenth the damage to the electric power system, which means that nearly 3,900 households are estimated to be without electric power on the first day after the earthquake. Repair of this system is anticipated to take much longer, so that seven days after the earthquake, still more than local 500 households are estimated to be without power.

Fire Following Earthquake
History shows that earthquake-induced fires have the potential to be the worst-case firesuppression scenarios for a community because an earthquake typically causes multiple ignitions distributed over a broad geographic area, with the potential to severely tax the local fire suppression agencies. Furthermore, if fire fighters are involved with search and rescue operations, they are less available to fight fires. Fire suppression efforts can also be limited by a water distribution system that has been impaired by the earthquake. Thus, many factors affect the severity of fires following an earthquake, including ignition sources, types and density of fuel, weather conditions, functionality of the water systems, and the ability of firefighters to suppress the fires. The principal causes of earthquake-related fires are open flames, electrical malfunctions, gas leaks, and chemical spills. Downed power lines may ignite fires if the lines do not automatically de-energize. Unanchored gas heaters and water heaters have in the past been common problems, as these readily tip over during strong ground shaking; State law however now requires new and replaced gas-fired water heaters to be attached to a wall or other support. This is expected to result in fewer overturned water heaters in future earthquakes.

The major urban conflagrations of yesteryear in major cities were often the result of closely built, congested areas of attached buildings with no fire sprinklers, no adequate fire separations, no Fire Code enforcement, and narrow streets. In the past, fire apparatus and water supplies were also inadequate in many large cities, and many fire departments were comprised of volunteers. Many of these conditions no longer apply to the cities of today. Nevertheless, major earthquakes can result in fires and the loss of water supply, as it occurred in San Francisco in 1906, and in Kobe, Japan in 1995. A large portion of the structural damage caused by the great San Francisco earthquake of 1906 was the result of fires rather than ground shaking.

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The moderately sized, M6.7 Northridge earthquake of 1994 caused 15,021 natural gas leaks that resulted in three street fires, 51 structure fires (23 of these caused total ruin) and the destruction, by fire, of 172 mobile homes. The 51 structure fires were caused by overturned water heaters (20), other overturned or damaged gas appliances (8), broken interior gas lines (8), broken gas meter set assemblies (2), street fires due to breaks in gas mains (7), and other unknown causes (8). The mobile home fires were primarily the result of failure of the supports leading to breakage of the gas risers, and breakage of the interior gas lines due to overturned water heaters and other appliances (Savage, 1995). The Southern California Gas Company reported 35 breaks in its natural gas transmission lines and 717 breaks in its distribution lines. About 74 percent of the leaks were corrosion related. In one incident, the earthquake severed a 22-inch gas transmission line and a motorist ignited the gas while attempting to restart his stalled vehicle. Response to this fire was impeded by the earthquake’s rupture of a water main; as a result, five nearby homes were destroyed. Elsewhere, one mobile home fire started when a ruptured transmission line was ignited by a downed power line. In many of the destroyed mobile homes, fires erupted when inadequate bracing allowed the houses to slip off their foundations, severing gas lines and igniting fires.

HazUS uses a Monte Carlo simulation model to estimate the number of ignitions and the amount of burnt area as a result of an earthquake. For the earthquake scenarios ran for Santa Monica, HazUS estimates between three and five ignitions immediately following an earthquake, with the San Andreas and Newport-Inglewood fault earthquake scenarios both triggering three (3) ignitions, and the Santa Monica fault triggering five (5) ignitions (Table 6-15). The burnt area resulting from these ignitions will vary depending on wind conditions; the scenarios assumed normal wind conditions of about 10 miles per hour (mph) or less. The models estimated that between 0.12 and

0.35 percent of the total area covered by the city (equivalent to between 0.01 and 0.03 square miles) would be burnt by the fires following the earthquake. If Santa Ana wind conditions are present at the time of the earthquake, the burnt areas can be expected to be larger.

Table 6-15: Fires Following an Earthquake
Earthquake Scenario No. of
Ignitions
Approximate
Burn Area
(% of city)
No. of Displaced
Individuals
Building Value
Destroyed
(Millions of $)
Santa Monica 5 0.35 407 80
Newport-Inglewood 3 0.12 80 21
San Andreas 3 0.12 78 20
Debris Generation
The models estimate that between 3 and 537 thousand tons of debris will be generated by the earthquake scenarios considered in this study (see Table 6-16). Of the total amount, brick and wood comprise between 29 and 50 percent of the total, with the remainder consisting of reinforced concrete and steel. If the debris tonnage is converted to an estimated number of truckloads, it will require 120 to 21,480 truckloads (assuming 25 tons per truck) to remove the debris generated by the earthquakes modeled. The largest numbers are associated with the Santa Monica earthquake scenario, and the smallest numbers with the San Andreas fault earthquake scenario. The Palos Verdes and Newport-Inglewood earthquake scenarios returned very similar estimates, although the Newport-Inglewood earthquake scenario has a higher percentage of brick/wood debris compared to the Palos Verdes fault earthquake scenario.

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Table 6-16: Debris Generated by Earthquake Scenarios
Earthquake Scenario Brick/Wood
(1000s Tons)
%
Total
Reinforced
Concrete/Steel
(1000s Tons)
%
Total
Total
(1000s
Tons)
No. of
Truckloads
Santa Monica 156 29 381 71 537 21,480
Palos Verdes 32.5 29 79.5 71 112 4,480
Newport-Inglewood 44 35 81 65 125 5,000
San Andreas 1.5 50 1.5 50 3 120

SEISMIC HAZARD MITIGATION ACTIVITIES
Existing Mitigation Activities
Existing mitigation activities include current mitigation programs and activities that are being implemented by county, regional, State, or Federal agencies or organizations.

California Earthquake Mitigation Legislation
California is painfully aware of the threats it faces from earthquakes. Since the 1800s, Californians have been killed, injured, and lost property as a result of earthquakes. As the State’s population continues to grow, and urban areas become even more densely built up, the risk will continue to increase. In response to this concern, for decades now the Legislature has passed laws to strengthen the built environment and protect the citizens. Table 6-17 provides a sampling of some of the 200 plus laws in the State’s codes.

Table 6-17: Partial List of the Over 200 California Laws on Earthquake Safety Government Code Section
8870-8870.95 Creates Seismic Safety Commission.

Government Code Section
8876.1-8876.10
Established the California Center for Earthquake Engineering Research.

Public Resources Code
Section 2800-2804.6
Authorized a prototype earthquake prediction system along the central San Andreas fault near the city of Parkfield.

Public Resources Code
Section 2810-2815
Continued the Southern California Earthquake Preparedness Project and the Bay Area Regional Earthquake Preparedness Project.

Health and Safety Code
Section 16100-16110
The Seismic Safety Commission and State Architect will develop a state policy on acceptable levels of earthquake risk for new and existing state-owned buildings.

Government Code Section
8871-8871.5
Established the California Earthquake Hazards Reduction Act of 1986.

Health and Safety Code
Section 130000-130025 Defined earthquake performance standards for hospitals.

Public Resources Code
Section 2805-2808 Established the California Earthquake Education Project.

Government Code Section
8899.10-8899.16 Established the Earthquake Research Evaluation Conference.

Public Resources Code
Section 2621-2630 2621. Established the Alquist-Priolo Earthquake Fault Zoning Act.

Government Code Section
8878.50-8878.52 8878.50.

Created the Earthquake Safety and Public Buildings Rehabilitation Bond Act of 1990.

Education Code Section
35295-35297 35295.

Established emergency procedure systems in kindergarten through grade 12 in all the public or private schools.

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Health and Safety Code
Section 19160-19169
Established standards for seismic retrofitting of unreinforced masonry buildings.

Health and Safety Code
Section 1596.80-1596.879
Required all child day care facilities to include an Earthquake Preparedness Checklist as an attachment to their disaster plan.

City of Santa Monica Codes
Implementation of earthquake mitigation policy most often takes place at the local government level. The City of Santa Monica Building and Safety Department enforces building codes pertaining to earthquake hazards. The City has adopted the provisions of the 2023 California Building Code, a modification to the 2022 Uniform Building Code with more restrictive amendments based upon the local geographic, topographic and climatic conditions. The City of Santa Monica, along with dozens of other local jurisdictions, have worked together to make these amendments to the California Building Code consistent with the rest of southern California.

The City of Santa Monica Planning Department enforces the zoning and land use regulations relating to seismic hazards. Generally, these codes and regulations seek to discourage development in areas that could be prone to seismic hazards, such as surface fault rupture, unstable slope areas, and areas susceptible to liquefaction; and where development is permitted, that the applicable construction standards are met. Developers in hazard-prone areas (other than surface fault rupture) may be required to retain a qualified professional engineer to evaluate the level of risk on the site and recommend appropriate mitigation measures. The Building and Safety Department is responsible for the enforcement of building, plumbing, electrical and mechanical codes. It also enforces ordinances and codes to ensure that buildings are safe by providing inspection services and plan check for new construction. The Building and Safety Department strives to protect the residents of a city by enforcing construction regulations.

Information about the City’s departments, codes and policies, handouts, bulletins, forms required for permit applications, fees, etc., are available from the City’s website. Look for the link to the City’s departments, and then refer to the Community Development Department, which oversees the City Planning Division and the Building and Safety Division and is responsible for the review of all development plans, permit issuance, zoning, and development-related applications (such as Conditional Use Permits) as well as the drafting and maintenance of City plans and codes. The Planning and Building and Safety Departments are listed and described under that link.

Community Development staff is also available to help at Santa Monica’s City Hall.

Businesses/Private Sector
Natural hazards have a devastating impact on businesses. In fact, according to the Institute for Business and Home Safety (IBHS), approximately 25 percent of all businesses do not reopen following a major disaster. Business owners and homeowners alike can protect their investment by identifying the risks associated with the natural and man-made disasters that their area is susceptible to (which this Plan covers), and then creating and implementing an action plan that defines the steps to take should a disaster strike. To help business owners with this effort, the IBHS has developed “Open for Business,” a disaster planning toolkit to help guide businesses in preparing for and dealing with the adverse effects of natural hazards (available from https://ibhs.org/BusinessDisasterRecovery/). The kit integrates protection from natural disasters into the business' risk reduction measures to safeguard employees, customers, and the investment itself.

The guide helps businesses secure human and physical resources during disasters, and helps to develop strategies to maintain business continuity before, during, and after a disaster occurs. The

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U.S. Small Business Administration also provides helpful information and checklists that can be used for this purpose (http://www.sba.gov/content/disaster-planning).

Hospitals
The Alfred E. Alquist Hospital Seismic Safety Act (“Hospital Act”) was enacted in 1973 in response to the moderate Magnitude 6.6 Sylmar Earthquake in 1971 when four major hospital campuses were severely damaged and evacuated. Two hospital buildings collapsed, killing forty seven people. Three others were killed in another hospital that nearly collapsed.

In approving the Act, the Legislature noted that “Hospitals, that house patients who have less than the capacity of normally healthy persons to protect themselves, and that must be reasonably capable of providing services to the public after a disaster, shall be designed and constructed to resist, insofar as practical, the forces generated by earthquakes, gravity and winds.” (Health and Safety Code Section 129680).

When the Hospital Act was passed in 1973, the State anticipated that, based on the regular and timely replacement of aging hospital facilities, the majority of hospital buildings would be in compliance with the Act’s standards within 25 years. However, hospital buildings were not, and are not, being replaced at that anticipated rate. In fact, the great majority of the State’s urgent care facilities are now more than 40 years old.

The moderate magnitude 6.7 Northridge earthquake in 1994 caused $3 billion in hospital-related damage and evacuations. Twelve hospital buildings constructed before the Act were cited (red tagged) as unsafe for occupancy after the earthquake. Those hospitals that had been built in accordance with the 1973 Hospital Act were successful in resisting structural damage. However, nonstructural damage (for example, plumbing and ceiling systems) was still extensive in those post-1973 buildings. Santa Monica Hospital Medical Center suffered about $15 million in immediate damage, forcing the tower building of the medical facility to close for nine months.

Saint John’s Hospital also suffered significant damage: its north wing, with 185 beds, the hospital nursery, and the neo-natal intensive care unit, were all immediately evacuated and moved to other parts of the facility. The hospital stayed open for three days before it was forced to shut down completely because of the extensive damage. On October 3, 1994, Saint John’s was again fully operational minus its north wing, which was demolished. The cost of repairs totaled $32 million.

Senate Bill 1953 (SB 1953), enacted in 1994 after the Northridge earthquake, expanded the scope of the 1973 Hospital Act. Under SB 1953, all hospitals were required by January 1, 2008 to survive earthquakes without collapsing or posing the threat of significant loss of life (life safety level). Provisions were made to allow this deadline to be extended to January 1, 2013 if compliance by the 2008 deadline would result in diminished capacity of healthcare services to the community. Subsequent amendments have provided for additional extensions, with the final date by which all hospitals must comply with the provisions of the act being January 1, 2020. To grant an extension to a hospital, the Office of Statewide Health Planning and Development (OSHPD) must consider the structural integrity of the building, the loss of essential healthcare services to the community if the hospital closed, and the financial hardship that the hospital would experience in complying with the provisions of the Act. The 1994 Act further mandates that all existing hospitals be seismically evaluated, and retrofitted, if needed, by 2030, so that they are in substantial compliance with the Act (which requires that the hospital buildings be reasonably capable of providing services to the public after disasters). SB 1953 applies to all urgent care facilities