If you felt a hard jolt this afternoon, followed by a short shake — then you were not alone. Perhaps you even felt more than one, or maybe even three.
A 4.0 magnitude earthquake hit the East Bay at 2:41 p.m. on Thursday, followed by a 1.8 magnitude quake at 3:09 p.m. and another quake, with a magnitude of 2.2 at 4:50 p.m. The initial quake was upgraded from a 3.9 to a 4.0 in magnitude after being reviewed by a seismologist, and had a depth of 6.1 miles, according to the U.S. Geological Survey.
The epicenter of the first earthquake was at College and Ashby avenues. The second hit on the Clark Kerr campus, . The third quake was off Tunnel Road. Keith Knudsen, deputy director of the USGS Earthquake Science Center in Menlo Park, said the strongest temblor was of the typical "strike-slip" variety, in which two sides of the fault slide horizontally.
The initial quake was short but strong, with a hard push followed by a rolling shake, and came only a few hours after California's ShakeOut drill. Schools around the state practiced their earthquake procedures during a fake quake at 10:20 a.m. Students and faculty at UC Berkeley participated in the ShakeOut, sounding a siren across campus this morning, school spokeswoman Janet Gilmore said.
At Berkeley High School, administrators and school safety staff inspected buildings around campus after this afternoon's quake hit and advised students and staff over the loudspeaker to stay in a secure space, "just as a precautionary measure," principal Pasquale Scuderi said. Scuderi said that earlier in the day, staff members had reviewed their disaster management plan, although the school did not participate in this morning's ShakeOut drill.
The first temblor created a large jolt in San Francisco's Civic Center area and was felt in parts of the region including Alamo, Sausalito, Clayton, San Leandro and Santa Cruz. Berkeley police said they have not received any reports of damage or injuries but have gotten some calls about car and building alarms that were activated by the quake.
Knudsen said there is a roughly 5 percent chance that this afternoon's quake could be a foreshock to a larger seismic event.
Bay City News contributed to this report