Expected Housing Losses in an Earthquake

San Andreas M7.8

In 2017, ABAG replaced previous housing loss numbers developed in 2003 with updated loss numbers. These numbers tell a compelling and personal story about the Bay Area’s potential future after an earthquake: how many buildings will be damaged? How many households will be displaced? And how many residents will be seeking shelter? These numbers use the most recent modeling techniques to identify potential residential housing losses for 16 plausible earthquake scenarios in the Bay Area. These numbers can be used to plan for retrofit programs, sheltering needs, and disaster recovery. Below are the major findings of the data.

The Bay Area could experience a wide variety of impacts from different scenarios across the region

Because of the region’s extensive network of earthquake faults, there are a number of plausible earthquake scenarios that could occur in the region. These scenarios vary widely in terms of magnitude, degree of shaking, and extent of shaking. Depending on the earthquake, any given jurisdiction could experience vastly different degrees of damage. And because the fault system is distributed throughout the region, nearly every corner of the Bay Area is at risk for experiencing damaging shaking in at least one of the earthquake scenarios modeled. Learn more about the probability of an earthquake that could affect your jurisdiction to determine which scenario to plan for.

Hayward M7.0

Hayward M7.0

Calaveras M7.0

Calaveras 7.0

Rodgers Creek M7.1

Rodgers Creek M7.1

West Napa M6.7

West Napa M6.7

San Andreas M7.8

San Andreas M7.8

Legend

Regional Summary of Earthquake Impacts to Residential Buildings

Scenario Earthquake Number of Displaced Households Number of People Seeking Short-Term Shelter Number of Uninhabitable Buildings Building Damage in Millions of Dollars
San Andreas (All Northern Segments) M7.8 198,700 51,600 68,900 28.4
San Andreas (Peninsula Segment) M7.2 121,100 31,100 40,500 17.1
Hayward (North & South) M7.0 145,000 42,000 55,100 20.9
Hayward South M6.8 115,700 33,300 41,800 16.2
Calaveras (All Segments) M7.0 68,700 19,100 25,500 11.0
Calaveras (Central Segment) M6.4 14,600 4,300 5,500 2.6
Rodger’s Creek M7.1 42,800 11,500 16,600 6.1
Concord – Southern Green Valley M6.8 40,200 11,300 16,700 6.8
San Gregorio M7.4 87,300 22,200 24,300 10.8
Maacama M7.4 8,800 2,300 3,800 1.4
Berryessa M7.1 9,100 2,500 3,300 1.4
Greenville M7.0 26,100 7,300 9,700 4.6
Great Valley – Segment 4b (Gordon Valley) M6.8 20,600 5,900 10,100 3.7
Great valley – Segment 5 (Kirby Hills) M6.7 18,200 5,400 8,200 3.3
Mount Diablo M6.7 45,900 12,000 18,200 8.0
West Napa M6.7 19,600 5,600 8,900 3.3

To download this data in Excel and GIS format, go to our Open Data Page.

Lots of residential buildings will be damaged

In any earthquake scenario, anywhere from a few thousand to nearly 70,000 residential buildings could be damaged to the degree that they are uninhabitable. The Loma Prieta earthquake caused a total of nearly 13,000 uninhabitable units in the Bay Area; most of the earthquake scenarios modeled will produce far more than this.

Uninhabitable Residential Buildings

Earthquake Scenario Alameda Contra Costa Marin Napa San Francisco San Mateo Santa Clara Solano Sonoma Total
San Andreas M7.8 8,300 1,400 3,100 200 18,300 19,300 15,500 400 2,400 68,900
Calaveras M7.0 9,000 4,400 200 100 1,700 1,000 8,700 300 100 25,500
West Napa M6.7 1,000 1,100 300 2,700 800 100 100 2,000 800 8,900

Building losses will vary between housing types

The distribution of single family, multifamily, and mobile homes damaged by an earthquake will vary based on the composition of the jurisdiction. In general, multifamily and manufactured homes are more likely to be significantly damaged than single family homes, but are less common. However, since multifamily buildings house more people, even though they are a smaller percentage of buildings damaged they may have a greater impact on the community.

Uninhabitable Residential Buildings by Housing Type

Earthquake Scenario Single Family Homes Multifamily Homes Manufactured Homes
  Count % of total Count % of total Count % of total
San Andreas M7.8 41,200 60% 21,200 31% 6,500 9%
Calaveras M7.0 15,800 62% 6,300 25% 3,100 12%
West Napa M6.7 4,700 53% 2,200 25% 2,000 23%

Significant assets will be lost

For many homeowners and building owners, their property is their largest asset. If residential buildings are damaged, this represents a huge loss of private assets in the region, particularly because many people do not have earthquake insurance. Loss of assets contributes to loss of population, as many homeowners will not be able to afford to rebuild their homes after such a large financial loss.

Residential Building Damage in Billions of Dollars

Earthquake Scenario Alameda Contra Costa Marin Napa San Francisco San Mateo Santa Clara Solano Sonoma Total
San Andreas M7.8 3,220 690 1,260 60 8,030 7,900 6,330 150 710 28,350
Calaveras M7.0 3,760 2,200 100 20 830 540 3,410 140 30 11,030
West Napa M6.7 430 560 180 690 340 100 60 680 290 3,330

Want more information, including next steps? Check out our Housing Loss White Paper. Download the data to do further analysis for your own jurisdiction.

Many households will be displaced from their homes

Homes that are significantly damaged will not be habitable following an earthquake. Many families will be displaced, causing them to seek shelter, stay with friends or family, camp in their backyards, or leave the region altogether. Many of those displaced will never return, especially renters and lower income residents. At the very least, displacement disrupts communities and significantly affects how residents meet their day-to-day needs and access jobs, health care, child care, and other services.

Displaced Households

Earthquake Scenario Alameda Contra Costa Marin Napa San Francisco San Mateo Santa Clara Solano Sonoma Total
San Andreas M7.8 25,400 3,600 6,200 300 69,600 42,200 47,200 700 3,500 198,700
Calaveras M7.0 22,100 8,300 400 100 10,600 2,800 23,800 500 100 67,700
West Napa M6.7 3,500 2,400 700 3,900 3,900 400 300 3,300 1,200 19,600

Not everyone who is displaced will seek shelter

A number of factors influence whether displaced residents will seek public shelter. Some residents will seek shelter even if their home is technically habitable; this may be due to fear about structural safety, aftershocks, or due to utility outage. Residents of multifamily buildings are more likely to seek shelter than single family homes. Ethnicity influences whether residents will seek shelter; Hispanic and Black households are assumed to be more likely to seek shelter. However, income is the largest factor in seeking shelter – lower income households are five times more likely to seek shelter than higher income households.

People seeking shelter

Earthquake Scenario Alameda Contra Costa Marin Napa San Francisco San Mateo Santa Clara Solano Sonoma Total
San Andreas M7.8 7,500 1,100 1,500 100 16,500 11,000 12,700 200 1,000 51,600
Calaveras M7.0 6,300 2,000 100 0 2,500 700 7,300 200 0 19,100
West Napa M6.7 1,000 700 200 1,200 900 100 100 1,100 300 5,600

Want more information, including next steps? Check out our Shelter Needs White Paper. Download the data to do further analysis for your own jurisdiction.

Seismic retrofit of older buildings is the best tool for reducing housing losses

A recent study found that for every $1 spent on mitigation, you can save $3 in earthquake losses. Retrofit also protects investments, keeps residents in their homes, and keep communities intact. The Resilience Program has several resources available for homeowners and local governments seeking to enact retrofit in their communities.

Resources to Learn More

For Governments

For Homeowners

Sources and Previous Reports

Last modified: 09.18.2018