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L.A. earthquake: 4.2 quake felt across Southern California [Updated]

September 1, 2011 |  3:41 pm

L.A. earthquake Sept. 1, 2011

Weak shaking from a magnitude 4.3 earthquake in the San Fernando Valley was felt as far away as the Grapevine and Orange County, according to the U.S. Geological Survey.

[Updated, 9:48 p.m.: The quake has been downgraded back to 4.2 from 4.3.]

But the shaking was not enough to cause damage. And the shaking was variable, depending on the neighborhood.

For example, Anthony Guarino, a seismic analyst at Caltech in Pasadena, said he didn’t feel the quake, but his colleagues across the street at the U.S. Geological Survey felt a sharp jolt.

The quake was centered in a highly seismic area in the mountains north of the Valley, near the same area where the 1971 Sylmar earthquake and the 1994 Northridge quake occurred, Guarino said.

“There’s a lot of faults in that area, very complex geology,” Guarino said.

He said there were at least five aftershocks following the 1:47 p.m. main quake.

The earthquake Thursday produced about 178 times less energy than last week’s East Coast quake, a magnitude 5.8 centered in Virginia, Guarino said.

Guarino said the quake offers a reminder to the public to drop, cover and hold on in the event of a large quake and not run outside like many East Coast people did.

“That’s one of the worst things to do,” Guarino said, because building facades are more likely to collapse onto people fleeing outside.

For example, he said, during the 2003 San Simeon earthquake in Central California, the only two people who died had run outside and were struck by falling debris.

Everyone else who stayed inside the shopping center during the 6.5 earthquake survived.

“Most buildings in California are built to code. But the facade of the building, there aren’t many codes. You may have chunks of plaster or concrete falling as you run outside,” Guarino said.


No major damage reported from 4.3 earthquake

L.A. earthquake: 4.3 magnitude quake hits San Fernando Valley

L.A. earthquake: No problems at Olive View-UCLA Medical Center

-- Rong-Gong Lin II

Map: Location of 4.3 magnitude earthquake in black brackets. Other small quakes appear in yellow. Source: U.S. Geological Survey