Resiliency

The Dangers of Housing Loss in an Earthquake

Earthquake Damage

This past fall, the four 2017 North Bay Wildfires damaged or destroyed an estimated 8,900 structures, taking out a major chunk of Santa Rosa’s (and the wider region’s) housing stock. It served as an uneasy reminder of the potential dangers the Bay Area and its residents face from other ever-present natural hazards, such as earthquakes. For example: How many buildings could be damaged? How many households displaced? How many residents in need of shelter?

A new page from ABAG’s Resilience Program, Expected Housing Losses in an Earthquake, provides the latest and greatest research findings about the region’s seismic risk – including the fact that up to 70,000 residential buildings could be made uninhabitable. In the below video, Dana Brechwald, Resilience Planner, discusses the research and details the residential building damage estimates and displacement risks for 16 different earthquake scenarios.

Key findings from the research include:

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.

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.

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.

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.

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.

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.

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.

Visit the page to learn more, review the data, and find additional resources for governments and homeowners. 

Key Documents

For more information, contact Dana Brechwald, Resilience Planner, at dbrechwald@bayareametro.gov

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