An earthquake of magnitude 7.2 to 7.5 would result in 3,000 to 18,000 deaths, 142,000 to 735,000 displaced households, and up to $250 billion in property damage, according to research by the U.S. Geological Survey and the Southern California Earthquake Center at the University of Southern California. The disaster would be the costliest in U.S. history.
The damage would be especially severe due to the fault's location under Los Angeles County and adjacent to Riverside and San Bernardino counties. In addition the fault runs under older, more vulnerable commercial and industrial structures.
By contrast, the most heavily shaken areas in the 1994 Northridge earthquake consisted mainly of wood-frame residential structures.
Estimated damages would also be greater than for a repeat of the historic 1857 San Andreas Fault earthquake.
The USGS and SCEC researchers developed hazard analysis software and used existing models from the Federal Emergency Management Agency to calculate losses. Their study appears in the May issue of Earthquake Spectra.
"One of the main goals of this study was to use our improved knowledge of seismic hazards in Southern California to evaluate and hopefully reduce the uncertainties in this type of risk analysis," said Thomas Jordan, director of SCEC and a study co-author.
The study analyzed 18 scenarios depicting potential shaking levels throughout the region. The loss estimates range widely because of the many variables involved, including the extent of a rupture on the fault, which was discovered in 1999.
The authors emphasize that a full Puente Hills fault rupture is a rare event. In 2003, a USC-led SCEC research team found that the fault had ruptured in earthquakes of magnitude 7.2 to 7.5 at least four times in 11,000 years.