San Jacinto fault unlikely to undergo major rupture, study says

A new study says people living near the San Jacinto Fault can breathe a little sigh of relief.

Shimon Wdowinski, a University of Miami associate research professor of geophysics, says the way the earth shifts along the San Jacinto Fault keeps significant pressure from building up in most places, leaving it less likely to have a major rupture.

Wdowinski's work appeared Sunday in Nature Geoscience magazine. He has been studying the fault on and off since 1991, when he was working at Scripps Institute of Oceanography at the University of California, San Diego.

"Seismic observations tell us what earthquakes happen and where they happen," Wdowinski said. "That's not the whole picture. There are also processes that don't generate earthquakes. Using very precise GPS and space-based radar, it's possible to monitor movements of a fraction of an inch per year."

Those measurements, Wdowinski said, allowed him to determine the San Jacinto is experiencing "deep creep," a term describing regular movement of the fault at a depth of about 15 miles.

The 130-mile fault zone runs through San Bernardino, Riverside, San Diego and Imperial counties in California.

"On the San Jacinto Fault, it breaks more often by smaller or moderate-sized earthquakes, 6.0, 6.5," he said. "The reason is the lower part of the fault releases a lot of the energy by small earthquakes."

Wdowinski said scientists are discovering that a standard fault model that has been used for years doesn't always work.

The importance of his study, he said, "is not all faults are the same."

E-mail Mark Muckenfuss at mmuckenfuss(at)PE.com.

(Distributed by Scripps Howard News Service, www.scrippsnews.com.)

Must credit The Press-Enterprise of Riverside, Calif.