Implications of the Northridge and Kobe Earthquakes for the National Earthquake Hazard Reduction Program

Abstract

T he Northridge earthquake of January 17, 1994 and the Kobe earthquake, which occurred one year to the day later on January 17, 1995 were both very damaging and disturbing events. The magnitude 6.7 Northridge earthquake occurred on a blind thrust fault that had not been identified as a potential seismic source, produced near-fault ground motions that were about 50% stronger than expected, and caused brittle failures in the moment frame connections of steel buildings located well away from the region of strongest shaking. Although the loss of life was moderate, in part due to its early morning occurrence, the earthquake caused direct losses estimated at about $30 billion. Although the magnitude 7 Kobe earthquake was not surprising geologically, it occurred on a relatively inactive fault in a region that conventional wisdom (and governmental policy) had grown to regard as being of low seismic risk. The scale of death and destruction...