BIG ONE MAY HIT AS SOON AS TODAY SAN ANDREAS STUDY CITES PENT-UP STRESS.

Byline: TROY ANDERSON Staff Writer

With more than 300 years of stress building on the San Andreas Fault, Los Angeles is long overdue for the ``Big One,'' according to new research published this month in the journal Nature.

The research by the Scripps Institution of Oceanography is among the most detailed yet and confirms a USC study that found pent-up stress along the southern end of the fault means it could rupture at any moment.

``All this data suggests that the fault is ready for the next big earthquake -- but exactly when the triggering will happen and when the earthquake will occur we cannot tell,'' said Yuri Fialko, an associate professor at the Institute of Geophysics and Planetary Physics at Scripps.

``It could be tomorrow or it could be 10 years or more from now.''

Fialko's research, using satellite and other data tracking, found the risk of a large earthquake -- magnitude 7.0 or greater -- may be increasing faster than researchers had previously believed on a 100-mile stretch of the fault southeast of San Bernardino. That section last erupted in 1690.

Experts say such a large earthquake could be 70 to 80 times more powerful than the 1994 Northridge Earthquake -- and would be strongly felt throughout much of Southern California, including Los Angeles County.

``It depends on how the earthquake ruptures,'' said Debi Kilb, a Scripps seismologist. ``If it goes from south to north, all the energy will be directed to the north, in which case Los Angeles will get hit pretty substantially.''

Ken Hudnut, a geophysicist at the U.S. Geological Survey in Pasadena, said simulations have found that thousands of people would be killed if such a blast of energy hit L.A.

``The damages would be immense,'' Hudnut said. ``The long-term impact in terms of business disruption would be quite significant.''

Local emergency preparedness officials say the L.A. area is probably the best-prepared region in the nation, but earthquake experts still note that possibly thousands of buildings throughout the county could collapse in such a large earthquake.

Thomas Heaton, a professor of engineering seismology at the California Institute of Technology in Pasadena, said officials have done a good job retrofitting unreinforced brick buildings and bridges, but that he is ``very unsatisfied'' with steps taken to retrofit thousands of poorly reinforced concrete buildings built before 1974.

``There may be some very important flaws in many of these older buildings,'' Heaton said. ``My guess is that a quarter to half of the older concrete buildings are in a state that I would not be comfortable having any of my family residing or working in those buildings.

``There is another issue that most of our steel-frame buildings have deficient welds in their joints and some simulations we have been doing indicates that makes them considerably prone to collapse. And no one is doing anything about that.''

Since Hurricane Katrina, Hudnut said, earthquake experts have been studying what kind of damage the ``Big One'' would cause to infrastructure the public relies on for food, water and other necessities trucked into L.A. across the fault line.

``A big San Andreas event would almost certainly do damage to the lifeline structures we count on,'' Hudnut said. ``We are reliant on engineering having been done properly.''

James Lott, executive vice president of the Hospital Association of Southern California, said the state's already overcrowded hospitals are not ready to deal with such a disaster.

``Our hospitals are operating year-round with an average daily census approaching 85 percent,'' Lott said. ``And so the numbers would be overwhelming.''

Lott said California hospitals are required to meet seismic standards starting in 2008 that would keep them up and running in a magnitude-7.0 or -8.0 earthquake -- but that price tag is at least $45 billion.

``The problem, of course, is that there is no funding for that,'' Lott said. ``Many hospitals are proceeding on track to meet the new requirements, but that's years down the road.''

In his research, Fialko found evidence that the southern San Andreas is mostly locked and continues to accumulate significant amounts of strain.

He calculated the rate at which the fault is moving and estimated the pace of plate movement at the fault at about an inch per year. That means that during the past 300 years the fault has accumulated about six to eight meters of slip ``deficit'' that will be released in a future earthquake.

If all the stress is released in one earthquake, it would result in a magnitude-8.0 earthquake, about the size of the 1906 San Francisco Earthquake that resulted in 3,000 deaths.

Michael Brooks, acting administrator for the county Office of Emergency Management, said police, firefighters and other first responders throughout the county are trained and prepared for such a large earthquake.

``Los Angeles County is well-prepared for a disaster, whether it be moderate or major,'' Brooks said. ``Does that mean the response will be perfect? Probably not.

``But particularly in light of (Hurricane) Katrina, we went back and looked at our emergency response plans to look for gaps. All the responders have been working very hard to ensure we address those gaps.''

troy.anderson(at)dailynews.com

[phone]