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5% chance bigger earthquake could hit after Yorba Linda temblor

August 29, 2012 |  5:22 pm

 There is a 5% chance that Wednesday's 4.1 earthquake in Yorba Linda could lead to something bigger in the next three days, U.S. Geological Survey seismologist Lucy Jones said.

There is "increased risk for the next few hours or days," Jones said. Most likely, the follow-up quakes would be smaller. A number of smaller aftershocks have already occurred.

Complicating matters, however, is that Wednesday's quake occurred near the Whittier fault, which is among the top 20 most dangerous faults in California, and has a potential of creating a magnitude 7 quake.

"On a normal basis, it's one of the potential sources of a bad earthquake," Jones said.

The Whittier fault runs for about 25 miles through Yorba Linda, Hacienda Heights and Whittier. It is considered to be among the more dangerous because the Whittier fault moves relatively fast, with a slip rate of 2 millimeters a year -- faster than the Newport-Inglewood, Hollywood or Santa Monica faults. (The San Andreas fault, by contrast, is considered to be California's No.1 dangerous fault.)

The 4.1 earthquake that jolted Yorba Linda on Wednesday afternoon appears to be an aftershock of the cluster of quakes that hit the region earlier this month, seismologists said.

The jolted area included southeastern Los Angeles County, Orange County and the Inland Empire. The quake occurred in about the same location of an earthquake doublet, two 4.5 quakes that occurred on Aug. 7 at 11:23 p.m. and Aug. 8 at 9:33 a.m. The area was also hit by a 4.0 quake on June 14.

Wednesday's quake, which hit at 1:31 p.m., was located near the center point of the magnitude-5.5 Chino Hills earthquake that reverberated through the Los Angeles Basin in the summer of 2008.


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