Scientists affiliated with the Southern California Earthquake Center (SCEC), one of 28 National Science Foundation (NSF) Science and Technology Centers, have released the results of a comprehensive study that identifies hot spots of seismic shaking in southern California.

"Considering all possible earthquakes, these are areas that we believe are going to shake more than other areas," says Tom Henyey, director of SCEC. The hot spots are southern California's large valleys and basins where the ground is flatter, the soil softer and the area more populous. While it has been known that sediment-filled valleys usually shake more than rock-hard mountain slopes during earthquakes, the SCEC study quantifies and refines how the local geology affects waves generated by earthquakes. The most important geologic factors, says Henyey, are the softness of rock or soil near a site’s surface and the thickness of sediments below a site.

Says James Whitcomb, deputy director of NSF's earth sciences division, which funds SCEC, "What's exciting is that these recently developed techniques can be applied to other parts of the U.S. and the world to reduce the destruction of earthquakes."

The SCEC study is published this month as a special volume of the Bulletin of the Seismological Society of America.