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PALM SPRINGS, Calif. - The notorious San Andreas fault might be on the cusp of producing a flurry of earthquakes that could rattle Southern California with a strong temblor every few decades or less, a geologist said Wednesday.
A detailed analysis of two periods of past quake activity on a section of the fault suggests a drawn-out period of little seismic activity might be coming to an end, said University of Oregon geologist Ray Weldon.
"Possibly we are at the point of switching from a period of time with a relative paucity of large and frequent earthquakes," Weldon said.
Weldon cautioned the switch could be decades away and that "flurry" is a relative term, since a cluster of quakes can strike over periods lasting 200 to 300 years. However, intervals as brief as 10 years have separated individual quakes in past clusters, he added. Details were presented Wednesday at the annual meeting of the Seismological Society of America.
Digging into the San Andreas at a location called Wrightwood about 60 miles northeast of downtown Los Angeles, Weldon and his colleagues found evidence of 30 quakes of magnitudes between 7.5 and 8.0 that had struck between 3000 and 1200 B.C. and 500 and the present.
An earthquake on the southern San Andreas of magnitude-7.5 or larger could kill thousands of people in the greater Los Angeles area and cause damage estimated in the tens of billions of dollars, experts have said.