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Seismic Hazards Assessment Program

Earthquakes can impact almost every aspect of life in California. In order to be better prepared for the inevitable future earthquake, the California Geological Survey (CGS) has several projects to help improve our understanding of California’s earthquakes, their likelihood and their effects, and to assure that we are building schools and hospitals to withstand earthquakes and other geologic hazards.
 

LIttle picture of a close up of the PSHA map

Probabilistic Seismic Hazards Assessment
Seismic hazards are calculated considering consensus values for earthquake rates based on earthquake history, fault slip rates, and site soil types. The seismic hazard information is combined considering the potential for earthquakes on all seismic sources, and the level of ground shaking that would be caused by those earthquakes. The result is expressed as the level of ground shaking (expressed as a percentage of gravity) that on average occurs every 500 years. These statewide estimates of seismic hazards can then be used to estimate the potential of future earthquake losses.

Little picture of Historic earthquake damage at Santa Rosa City Hall, 1906

Historical Earthquakes (and Earthquake Catalogs)
Studies of historic earthquakes provide basic background for projecting future seismic hazards and losses. A map of historic earthquakes of greater than Magnitude 5.5 and earthquake catalogs. Lists of significant California earthquakes and earthquake anniversaries are available here.

Little picture of annuallzed loss by county in California

Loss Estimation
Estimating damage done from future earthquakes.

Cartoonish picture of a school

Hospital/School/Environmental Reviews
CGS reviews a number of environmental documents and provides comments relating to geologic hazards and issues that apply directly to assessing the potential impacts of land-use modification.  As part of this process, CGS  provides site reviews on consulting reports in geology, seismology, and geotechnical engineering for public school and hospital construction.