March 25, 2009

Could quake series set off the big one?

A series of small earthquakes like the ones that have shaken Southern California this week has a 5 percent chance of triggering a major quake, experts say.

The tremors have occurred in the Salton Sea area east of San Diego, The San Diego Union-Tribune reports. Most have been too small to feel but a temblor early Tuesday measured 4.8 on the Richter scale, big enough to be felt and heard, although unlikely to cause damage.

The area is near the southern end of the San Andreas Fault, Neal Driscoll of the Scripps Institution of Oceanography, said to the newspaper. The fault runs from the Salton Sea area north, ending under the Pacific west of Eureka, Calif., and Driscoll said that the southern end is more than a century overdue for a major quake.

Morgan Page of the U.S. Geological Survey told the Union-Tribune that a quake as large as Tuesday's has a 5 percent chance of setting off a major one but, he said, that the odds of a quake drop sharply with time.