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Pair Of Earthquakes Jolt San Francisco Bay Area

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CBS 5 seismograph registering a magnitude 3.9 earthquake centered near Berkeley at 8:16 p.m. on October 20, 2011. (CBS)

CBS 5 seismograph registering a magnitude 3.9 earthquake centered near Berkeley at 8:16 p.m. on October 20, 2011. (CBS)

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BERKELEY (CBS 5 / KCBS) — A pair of earthquakes, with magnitudes of 4.0 and 3.8 respectively, rattled the San Francisco Bay Area on Thursday afternoon and evening, but local police agencies said there were no reports of serious damage or injuries.

Both quakes were centered near Berkeley with depths of around six miles. The 4.0 temblor occured at 2:31 p.m., followed by a 3.8 temblor nearly six hours later at 8:16 p.m., according to the U.S. Geological Survey.

USGS seismologist Jack Boatwright said the first one was a “sharp little earthquake” that had a “very nice impulsive character.” Other USGS scientists described the second quake as an aftershock.

>> Related Content: Special Earthquakes Section

Based on USGS maps, the quakes’ epicenters appeared to be beneath the University of California Berkeley’s Clark Kerr campus.

Both temblors created large jolts throughout the East Bay that were also felt across the bay in San Francisco — most notably shaking the city’s Civic Center area. The quakes were also felt in other parts of the region including Sausalito to the north and as far south as Santa Cruz.

“(There was) a medium jolt, then a significant low frequency shake for more than 5 seconds — by far the biggest in the 18 years I have lived here,” Foster City resident Jeff Arcuri said, in describing the nighttime quake to CBS 5.

“It was a nice jolt,” agreed Diane Coppini, who said the evening temblor was strong enough to knock photographs off the wall and glasses onto the floor at her Emeryville home.

Keith Knudsen, deputy director of the USGS Earthquake Science Center in Menlo Park, said Thursday’s temblors were standard Hayward Fault Line quakes of the typical “strike-slip” variety, in which two sides of the fault slide horizontally.

“We live on Hayward Fault and felt a rolling motion,” said resident Edward Berini in one of many e-mails sent to CBS 5 in the minutes after the first quake occured.

“My apartment shook for a couple of seconds,” e-mailed Melanie Johnson from downtown San Francisco, while Craig Cannon in Martinez wrote, “Felt it real good upstairs at home. It felt like one of those old fashioned massage beds.”

KCBS’ Chris Filippi Reports:

Staff members at the Rockridge Branch Library in Oakland said that a rumbling sound could be heard right before the first quake hit and sent a few pieces of mounted artwork askew.

“It was very dramatic here — the building shakes every time a truck goes by — so everyone in the building noticed it,” said Erica Siskind, a children’s librarian.

At Saul’s Restaurant and Deli in Berkeley, restaurant manager Taci Traverso said she also “heard it coming.”

“It’s hard to describe, but I was sitting on the sidewalk and I felt a rumbling sound before I felt the vibration,” she said.

Tami Humphrey, director of a pre-school just north of Berkeley, said she was outside with her students when the afternoon quake struck: “We felt it pretty good. It felt like a drop and then a shake.”

All Bay Area Rapid Transit trains were halted for about 15 minutes after each quake, BART officials said, as train operators conducted track inspections. No damage was found.

The USGS’ Knudsen said there was roughly a 5 percent chance that Thursday’s quake activity could be a foreshock to a larger seismic event, which San Francisco Mayor Ed Lee called “another reminder that we have to be prepared.”

The jolts were felt almost 22 years to the day after the Loma Prieta earthquake struck the Bay Area during the 1989 World Series. The magnitude 6.9 quake killed 63 people, injured almost 3,800 and caused up to $10 billion damage.

>> Photo Gallery: 1989 Loma Prieta Earthquake Damage

>> Photo Gallery: 1906 Great San Francisco Earthquake Damage

Thursday’s quakes also occurred on the same day that more than 8.5 million people participated in the state’s annual earthquake drill known as the Great California Shake Out.

(Copyright 2011 CBS San Francisco. All rights reserved.)

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