Researchers Outline Impact Of Rupture In Puente Hills Fault
NCB 4 | May 25, 2005
LOS ANGELES -- If the Puente Hills fault -- which was not recognized as a major active fault until 1999 -- ruptures, the resulting earthquake could devastate a large area of the Southland, scientists said Wednesday.
Images: Researchers Present Findings
Seismologists now know that the fault has ruptured at least four times in the last 11,000 years, resulting in earthquakes with magnitudes ranging from 7.2 to 7.5, according to the U.S. Geological Survey and USC-based Southern California Earthquake Center.
A similar earthquake there today could cause 3,000 to 18,000 deaths, 60,000 to 260,000 injuries and $250 billion in total damages, according to Tom Jordan, director of the SCEC and co-author of a study on the fault published in the May issue of Earthquake Spectra.
Between 142,000 and 735,000 people could be displaced if such a temblor hits.
"There are a lot of uncertainties in these predictions," said Jordan, explaining the wide range in possible deaths, injuries and displacements.
The Puente Hills fault largely runs in an east-west direction. On the western end, it is a couple miles underground, almost directly under USC, said Jordan. The fault continues eastward, dipping under the San Gabriel Mountains.
In determining probable losses related to a Puente Hills fault-related quake, scientists created 18 scenarios depicting different possible shaking throughout the region.
The scenarios all assumed an earthquake occurring at 2 p.m. during a weekday, when Southlanders are at work. The number of casualties would be "significantly less" if the quake hit at night, when most people are home, researchers said.
The magnitude-6.7 Northridge earthquake in 1994 resulted in 37 fatalities directly related to the temblor.
The predicted losses from a Puente Hills quake are far greater, in part because of the higher potential magnitudes. Also, the Puente Hills fault sits under old and more vulnerable commercial and industrial structures, while the Northridge quake shook up an area of wood-frame residential structures.
While most of the damage would be in Los Angele County, residents of San Bernardino and Orange counties -- on the east and south ends of the fault -- may also be affected.
Scientists say that a full Puente Hills fault rupture is rare, occurring once every 3,000 years.
You have a much greater chance of dying in an auto accident than being killed by an earthquake, said USGS researcher Ned Field.
"That being said," Field said, "there are other sources of earthquakes throughout the region, and it's not (a) question of if, but when, so everyone should take necessary safety precautions.
"With USGS science, we are striving to prevent these natural hazards from becoming disasters. We live in earthquake country and therefore should always be prepared."