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Far Fewer Casualties Expected in Big Quake : Research: Study projects twice the economic damage. Lessons from Loma Prieta, Northridge temblors included.

August 16, 1994|ROBERT LEE HOTZ | TIMES SCIENCE WRITER

The most serious earthquake expected during the next 50 years should cause half the casualties but almost twice the economic damage in Los Angeles, San Francisco and Tokyo than had been predicted, according to new projections released by Stanford University earthquake experts today.

The new damage estimates are the most detailed in nearly a decade, experts said. The figures significantly recast the risks posed by a major temblor to people and businesses in the three areas as well as to the banks and insurance companies that will partially cover their losses.

The estimates are the first to incorporate the lessons of the magnitude 7.1 Loma Prieta earthquake that struck the San Francisco Bay Area in 1989 and the magnitude 6.8 Northridge quake that shook the Los Angeles Basin on Jan. 17. The Northridge earthquake killed at least 61 people and caused more than $20 billion in damage.

People living and working in the Los Angeles area, according to the new estimates, can expect a magnitude 7 earthquake along the Newport-Inglewood Fault to cause 2,000 to 5,000 deaths and an economic loss ranging from $125 billion to $145 billion. The fault, the largest in the area, runs along the coast from Newport Beach through Culver City.

As many as 15,000 people could be hospitalized with injuries, the scientists estimated.

The projections are the result of worst-case scenarios that assume that the earthquakes in the three metropolitan areas--the largest considered likely in the next 30 to 50 years--would strike as closely as possible to highly developed areas.

The new study also showed that a repeat of the famous 1906 8.3-magnitude temblor on the San Andreas Fault near San Francisco could kill between 2,000 and 6,000 people and cause an economic loss in excess of $115 billion.

A recurrence of the Great Kanto earthquake that destroyed Tokyo in 1923, killing 140,000 people, would today cause between 40,000 and 60,000 deaths, the scientists said. Property damage and economic losses, however, could run from $800 billion to $1.2 trillion, large enough that world financial markets, stock prices and interest rates would be affected as the Japanese withdrew overseas investments in order to rebuild.

The researchers said they were not trying to predict the likelihood of such an earthquake, but were attempting to develop a more reliable yardstick for measuring potential damage from a major natural disaster.

For all three scenarios, "the casualty numbers have gone down considerably and the estimate of property damage has increased by a factor of two," said Haresh Shah, chairman of the Stanford civil engineering department, who helped prepare the estimates.

The casualty estimates vary depending on what time the hypothetical earthquake occurs. Injuries in the Northridge quake were low in part because it occurred before dawn when office buildings and freeways were deserted. Increasingly stringent building codes also are helping to reduce the overall risk. The researchers' lower estimates of death and injury "reflect the fact that we have been pretty successful in engineering our structures to protect lives," Shah said.

But the magnitude of the potential economic damage is a different matter. "We have used newer knowledge and the numbers come out much bigger," he said. "We have seen that the damage is always a little higher than the old data indicated."

In part, the economic consequences of a major earthquake were found to be higher than earlier studies because the researchers placed greater weight on the cost of interrupted business and lost time from employees unable to report for work because of injuries or transportation difficulties.

The damage estimates were prepared by a team of Stanford researchers led by Shah, and a private group called Risk Management Solutions, which evaluates earthquake risks for industry, insurance companies and the federal government.

"In general, the insurance and the banking communities are taking natural disasters much more seriously these days," said Tom Hutton, president of Risk Management Solutions. "There would certainly be (insurance) companies that would not withstand the events that we have projected."

Since the Northridge quake, which damaged more than 86,000 structures and caused about $6 billion in insured losses, two large California insurers have announced that they will no longer write earthquake coverage.

The best-known federal damage projections for Los Angeles earthquakes have attempted to gauge the potential havoc wreaked by a hypothetical "Big One"--a magnitude 8.3 temblor along the southern end of the infamous San Andreas Fault. A landmark federal study prepared in 1981 at the request of the National Security Council estimated that such a quake would kill between 3,000 and 14,000 people, depending on the time of day it occurred, hospitalize up to 55,000 people and cause about $20 billion in property damage.

Subsequent research has led earthquake experts to believe that a less powerful quake along the Newport-Inglewood Fault would cause greater damage to the heavily populated portions of the metropolitan area than an 8.3 temblor on the San Andreas.

The researchers prepared their estimates with a relatively new computer-mapping system that allowed them to combine information about individual structures with local geological conditions, such as soil type, fault lines and slope, which influence the severity of the ground shaking in an earthquake.

The computer database contains information about every one of the 6 million homes in California, the soil type on which they sit and all known fault lines.

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