Earthquake loss estimation and planning scenarios quantify seismic risk based on seismic hazard and exposure and vulnerability of the built environment. Such studies need to be frequently updated because of continuing development of the built environment and evolving technology in earthquake ground motion prediction and seismic hazard assessments. California Geological Survey (CGS) has developed and participated in the development of many planning scenarios since 1980. CGS also updates its scenario- and probabilistic-based loss estimations when significant developments occur in ground motion hazard analyses and in built environment.
Using the latest Hazus default information for built environment and demographics, CGS updated statewide annualized earthquake losses (AEL) for California. This AEL update is based on ground motions from the 2014 update of the U.S. Geological Survey National Seismic Hazard Model. It incorporates the effect of local soil conditions using a new semi-empirical nonlinear site amplification model and an updated map of time-averaged shear-wave velocity in the upper 30 m. AELs are estimated at four levels of geographic resolution: census tract, county, metropolitan statistical area (MSA), and incorporated cities. AEL estimate at the state level is ∼3.7 billion. Over 70% of the projected loss is contributed by three MSA’s: Los Angeles-Long Beach-Santa Ana, San Francisco-Oakland-Fremont, and Riverside-San Bernardino-Ontario. Los Angeles County, with its very high economic exposure and population in addition to its proximity to many of the most seismogenic faults in the country, has an estimated AEL of ∼$1.14 billion, representing over 30% of the state AEL and exceeding AEL estimates for all other states in the conterminous U.S. (see a brief
summary or Chen et al., 2016, below.)
Using HAZUS default information for built environment and demographics, CGS studied statewide annualized earthquake losses (AEL) based on standard seismic hazard models developed by CGS and United States Geological Survey (USGS) for the National Seismic Hazard Maps. The annualized loss estimation incorporated the effect of local soil conditions using current ground motion prediction equations. AELs were estimated at three levels of geographic resolution: census tract, county, and Metropolitan Statistical Area (MSA). Our calculations show that the lower ground motions predicted by the newer ground motion prediction equations translate directly to substantially lower annual earthquake loss estimations in California
(see a brief
summary or download
CGS Special Report
CGS studied potential losses due to scenario earthquakes. Each scenario includes estimates of damage, casualties and other consequences of the scenario earthquake. In northern California the three most damaging scenario earthquakes involve co-seismic rupture of different combinations of segments of the San Andreas Fault, with estimated economic losses ranging from nearly $70 billion to over $80 billion. In southern California, the most damaging scenario is the M7.1 earthquake on the Puente Hills Fault, with up to 30% building loss in some census tracts and total predicted building loss of $79 billion ($82.8 billion in total economic loss). Similarly to the results for AEL, calculated losses for scenarios are significantly lower when current ground motion prediction equations are used to develop the scenario ground shaking.
The 2009 work was supported by California Emergency Management Agency (see a brief
project report or
CGS Special Report
CGS estimated scenario earthquake losses in ten counties in the San Francisco Bay Area and in ten counties in Southern California using scenario ground motions of fifty potential earthquakes published by the United States Geological Survey (USGS). CGS also estimated statewide annualized earthquake losses using the
2002 PSHA maps for the State of California, prepared and published by CGS and USGS. These analyses used HAZUS Service Release 2
default information for built environment and demographics.
a loss estimation software package developed by the Federal Emergency Management Agency. The 2005 work was supported by CGS. For major findings, links to the detailed results for all earthquake scenarios and for statewide annualized earthquake losses, and for detailed technical discussions see "Estimation of Future Earthquake Losses in California".
Other CGS Publications
Chen, R., K.S. Jaiswal, D. Bausch, H. Seligson, and C.J. Wills (2016). Annualized Earthquake Loss Estimates for California and Their Sensitivity to Site Amplification,
Seismological Research Letters, v 87 (8), Pre-Issue Publication Article, doi: 10.1785/0220160099.
Jaiswal, K.S., D. Bausch, R. Chen, J. Bouabid, H. Seligson (2015). Estimating annualized earthquake losses for the conterminous United States,
Earthquake Spectra, v 31 (S1), S221-S243.
Chen, R., D.M. Branum, and C.J. Wills (2013). Annualized and scenario earthquake loss estimations for California,
Earthquake Spectra, v 29 (4), 1183-1207.
Cao, T. (2007). Disaggregation of seismic hazard extended to disaggregation of annualized loss ratio,
Bulletin of the Seismological Society of America, v 97 (18), 305-317.
Cao, T. and M.D. Petersen (2006). Uncertainty of earthquake losses due to model uncertainty of input ground motions in the Los Angeles area,
Bulletin of the Seismological Society of America, v 96 (2), 365-376.
Cao T., M.D. Petersen, C.H. Cramer, T.R. Toppozada, M.S. Reichle, and J.F. Davis (1999). The calculation of expected loss using probabilistic seismic hazard,
Bulletin of the Seismological Society of America, v 89 (4), 867-876.
Earthquake Planning Scenarios published by the California Geological Survey