New map of earthquake hazards


  • Michael Carlowicz


After three years of compiling data from more than 500 faults and applying new hazard assessment techniques, the U.S. Geological Survey (USGS) has produced new seismic hazard maps for the continental United States. The map shown here provides estimates of earthquake ground accelerations (as a percentage of g, the acceleration of a falling object due to gravity) having a 10% probability of being exceeded in 50 years. The map is based on seismicity and fault-slip rates, and it accounts for the frequency of occurrence of earthquakes of various magnitudes. According to the USGS and the California Department of Conservation, which collaborated on a joint hazard assessment for California, more than 70% of California's population lives in an area where high levels of ground shaking could occur in the next 50 years.