Earthquake

Earthquakes are of great concern in Southern California, and while the potential earthquake hazards depend upon your location, California is considered at higher risk compared to the rest of the country. In fact, Los Angeles County alone carries about 25% of the earthquake loss risk of the entire nation. In this light, the Multi Hazards Project has worked extensively in this area.

The ShakeOut Scenario

The ShakeOut Scenario, completed in May, 2008, is the first major product of the USGS Multi-Hazards Demonstration Project. This scenario designed a plausible earthquake on the southern San Andreas Fault and then studied its effects, from the direct physical impacts to the long-term, social, cultural, and economic consequences. Immediately after publication, it was clear that the ShakeOut Scenario has made a difference. It has identified key strengths and vulnerabilities in southern California’s readiness for major earthquakes, and this has already launched discussions that are the first step toward addressing problems. It has encouraged new discoveries and applications in research fields as diverse as earthquake physics and disaster economics, broadening the foundation for future advances. And it has inspired the largest ever participation in earthquake preparedness drills, among both the emergency response community and the general public, across the country and around the globe.

The ShakeOut Scenario considered impacts to an eight-county region (Riverside, San Bernardino, Los Angeles, Orange, Ventura, Kern, San Diego, and Imperial Counties). Beginning in the summer of 2008, additional research was be conducted to evaluate the earthquake’s impacts for particular communities and stakeholders.

Golden Guardian Exercises

In May 2008, ShakeOut Scenario scientists handed off their results to planners developing November response exercises. ShakeOut Scenario scientists remain engaged in the exercise planning process, to make sure that planners have the tools and information they need to make full use of the ShakeOut Scenario. Again, in 2012, the ShakeOut Scenario will be the scenario used for California’s Golden Guardian Exercise.

Business Impacts & Planning

As part of the results of the ShakeOut Scenario, the Bureau of Labor Statistics released a report highlighting the impacts to employers and jobs across southern California. That Special Report, released in June of 2011, can be found here.

Support was also lent to the development of resources for businesses at part of ShakeOut found here.

Recovery from the ShakeOut Earthquake

Recovery from an earthquake like the M7.8 ShakeOut Scenario will be a major endeavor taking many years to complete. Hundreds of Southern California municipalities will be affected; most lack recovery plans or previous disaster experience. To support recovery planning, experts studied two southern California communities in detail: Torrance and Palm Springs. They then extended the regional ShakeOut Scenario analysis into the recovery period using a recovery model, 2) localized analyses to identify longer-term impacts and issues in these two communities, and 3) considered the regional context of local recovery. Key community insights about preparing for post-disaster recovery include the need to: geographically diversify city procurement; set earthquake mitigation priorities for critical infrastructure (e.g., airport), plan to replace mobile homes with earthquake safety measures, consider post-earthquake redevelopment opportunities ahead of time, and develop post-disaster recovery management and governance structures. This work also showed that communities with minor damages are still sensitive to regional infrastructure damages and their potential long-term impacts on community recovery. This highlights the importance of community and infrastructure resilience strategies as well. The published results are here.

Largest Aftershocks

The ShakeOut Scenario project generated realistic simulations of aftershock sequences. Some of these aftershocks will be larger and potentially more devastating than the 1994, magnitude 6.7 Northridge earthquake. For certain large aftershocks that will be part of the Golden Guardian exercises, ShakeOut scientists are creating estimates of shaking and consequences.

SoSAFE Underway

The goal of SoSAFE (Southern San Andreas Fault Evaluation) is to reduce the uncertainty in earthquake hazard by determining the rupture chronology and slip rates of the Southern San Andreas fault system for the last 2,500 years. A planning workshop was held in January 2007 to prioritize the research plan. Early results appear promising in several areas. First, the Frazier Mountain site has yielded new evidence for 4-5 past events and datable layers has been sampled. Second, dates from the Coachella site and Bidart site have allowed new interpretations of event evidence in the Coachella Valley and Carrizo Plain. A second major SoSAFE workshop was held in Palm Springs on September 9, 2007, at which time initial results from SoSAFE’s first year of funding were presented.

When designing the ShakeOut earthquake, the ShakeOut Scenario was able to take advantage of the expertise assembled at SoSAFE workshops.

Earthquake Early Warning

Late in 2007, MHDP participated in discussion with Caltech, U.C. Berkeley, and the USGS to create an Earthquake Early Warning System.  As contributors and end-users have considered the results of the ShakeOut Scenario, the discussion about earthquake early warning has been re-engaged, in examining how it might mitigate injury, property damage, and the loss of life in the ShakeOut earthquake.

Currently, work is being done in partnership with the California Integrated Seismic Network (CISN) to develop the tools and algorithms to provide a warning that an earthquake is underway and strong shaking will reach you based on your distance from the fault rupture.