A little-known fault may cause unprecedentedly damaging earthquake in Los Angeles, US scientists projected on Wednesday.
However, the probability of such an earthquake along the Puente Hills fault is really small. As an individual the odds of dying of a heart attack or an auto accident are much greater than of dying from this earthquake, noted scientists from US Geological Survey ( USGS) and the Southern California Earthquake Center.
The 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.
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 US dollars in property damage, according to this study. The disaster would be the costliest in US history, the study shows.
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. Estimated damages would be greater than for a repeat of the historic 1857 San Andreas Fault earthquake.
"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, 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 note that a full Puente Hills fault rupture is a rare event. In 2003, a 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.
"That being 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," sayid first author Ned Field.
He added that because a Puente Hills earthquake would have widespread impact, emergency and public policy officials should plan accordingly.
The loss projections assume that no efforts will be made to reduce the vulnerability of structures in the area. But if society chooses to invest in mitigation, many of these losses could be avoided, the researchers said.
The research team arrived at its estimates by averaging losses predicted under each scenario and model, which all assumed an earthquake occurring at 2 p.m. during a weekday, when many people are at work.
The number of casualties would be significantly less if an earthquake were to occur on the fault at night, when most people are at home, scientists said.
Their findings also include:
-- The total number of injuries could range between 56,000 and 268,000, with an average of about 120,000.
-- The number of displaced households would range from 142,000 to 735,000, with an average of 274,000.
-- Relief agencies would have to provide short-term public shelter for 42,000 to 211,000 individuals, with an average of 80, 000.
-- The quake would create between 30,000 and 99,000 tons of debris, with an average of 51,000 tons.