Swarm of small quakes rattles San Ramon area

SAN RAMON, Calif. (KGO) -- San Ramon has had more than 20 small earthquakes in the past 20 hours, which is quite the coincidence because Thursday is the Great California Shakeout, a day to bring attention to earthquake preparedness.

The quakes keep shaking the East Bay city. The latest was a 2.6 magnitude quake at 3:44 p.m. The biggest Wednesday just a bit over magnitude 3.0.

Residents said they felt the largest quake, a magnitude 3.2, among a swarm of at least 20 little ones.

"It woke me up. I was sleeping," said one resident.

University of California Berkeley Seismological Laboratory scientists were keeping a close watch on this most recent swarm.

"It is going to be broadly felt. You'll hear a snap crash," said Dr. Peggy Hellweg, a UC Berkeley seismologist.

Seismologists say they've seen it before in the region and describe the abnormality as being well within the range of acceptable normalcy.

"We have definitely had similar swarms along the Calaveras fault, Alamo, Danville, Pleasanton," Hellweg said.

It's the Pacific Plate grating past the North American Plate at the junction of the Calaveras and Hayward faults five miles below the surface. The largest measurement associated with such movement, magnitude 4.5.

Hellweg said a 4.5 magnitude quake would not surprise her, but something larger like a 5 would.

Such movement would definitely jiggle if not spill your coffee or drink, but it still would not be the proverbial big one.

"I mean if it is going to happen it will happen. I cannot control it," said Tennaye Armitage, a San Ramon resident.

And that's what you call being underwhelmed in earthquake country.

Anyone who wants to try out the mobile earthquake simulator, the Big Shaker, can at at Frank Ogawa Plaza in Oakland Thursday from 6 a.m. to at least 2 p.m.

Quake Resources