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Southern California is overdue for 'The Big One,' study finds

August 20, 2010 | 11:11 am
Evidence of the 1857 Ft. Tejon quake is evbident on the side wall of this trench at the Bidart Fan. This area in the Carrizo Plain is one of the easiest places to see movement on the San Andreas Fault.

UC Irvine postdoctoral scholar Sinan Akciz, left, and J. Ramon Arrowsmith, a geologist at Arizona State University, right, work with Lisa Grant Ludwig on mapping the history of temblors on a portion of the San Andreas Fault.Southern California is overdue for a major earthquake along the San Andreas fault, according to a landmark study released Friday.

The long-awaited study came after scientists spent years studying the geology of the Carrizo Plain area of the San Andreas, which is about 100 miles northwest of Los Angeles. It found that earthquakes along the San Andreas fault have occurred far more often than previously believed.

"What we know is for the last 700 years, earthquakes on the southern San Andreas fault have been much more frequent than everyone thought," said UC Irvine researcher Sinan Akciz said in a statement. "Data presented here contradict previously published reports."

Added UCI researcher Lisa Grant Ludwig: "People should not stick their heads in the ground. There are storm clouds gathered on the horizon. Does that mean it's definitely going to rain? No, but when you have that many clouds, you think, 'I'm going to take my umbrella with me today.' That's what this research does: It gives us a chance to prepare."

The last massive earthquake on that part of the fault occurred in 1857. But researchers from UC Irvine and Arizona State University found that earthquakes have occurred as often as every 45 to 144 years.

That would make the region overdue for the type of catastrophic quake often referred to as "The Big One."

The finding adds weight to the view of many Southern California seismologists that the San Andreas has been in a quiet period and that a major rupture is possible.

The research, published Friday in the journal Geology, used charcoal samples to look for earthquake activity going back centuries.

-- Rong-Gong Lin II

Updated, 6:21 p.m.: Study shakes up scientists' view of San Andreas fault earthquake risk

Top photo: Evidence of the 1857 Ft. Tejon quake is evident on the side wall of this trench at the Bidart Fan. This area in the Carrizo Plain is one of the easiest places to see movement on the San Andreas Fault. Bottom photo: UC Irvine postdoctoral scholar Sinan Akciz, left, and J. Ramon Arrowsmith, a geologist at Arizona State University, right, are seen in 2009 as they work with Lisa Grant Ludwig on mapping the history of temblors on a portion of the San Andreas Fault. Credit: Ricardo DeAratanha / Los Angeles Times

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