Southern California rattled by two 4.5 quakes within 10 hours

Reuters News
Posted: Aug 08, 2012 1:47 PM
Southern California rattled by two 4.5 quakes within 10 hours

By Steve Gorman

LOS ANGELES (Reuters) - A pair of moderate earthquakes, both registering a magnitude 4.5, struck the Southern California town of Yorba Linda on Tuesday night and Wednesday, rattling the region twice within 10 hours, but no damage or injuries were reported.

The latest quake was recorded shortly after 9:30 a.m. (12:30 p.m. EDT) 2 miles northeast of Yorba Linda, an affluent Orange County community southeast of Los Angeles that was the birthplace of the late former President Richard Nixon and houses his presidential library and museum.

It was centered about 5.5 miles beneath the surface. The earlier temblor occurred at about 11:20 p.m. on Tuesday in about the same area at roughly the same depth, and was followed by more than a dozen smaller aftershocks overnight, according to the U.S. Geological Survey.

Seismologists at USGS and the California Institute of Technology in Pasadena said the twin quakes, called "doublets," occurred near the so-called Whittier fault, one of the larger underground fissures running through Southern California.

But they said the precise origin of the quakes could not immediately be determined because neither was strong enough to create a rupture at the surface.

In Yorba Linda, a town of about 66,000 near the epicenter, city spokesman Mark Aalders said the first quake produced more of an initial jolt, "but today it seemed to linger longer."

He said there were no reports of damage or emergency calls related to seismic activity.

Earthquakes measured at 4.5 typically generate too little ground motion to cause property damage, and quakes of all sizes tend to occur in clusters, experts said.

"I don't think it's particularly unusual," Caltech seismologist Kate Hutton told Reuters. "It's part of Southern California's normal earthquake activity."

(Editing by Cynthia Johnston and Sandra Maler)