By Marcus Wohlsen and Terry Collins, Associated Press
BERKELEY, Calif. (AP) -- Two small earthquakes hit the San Francisco area Thursday, jolting residents on the same day many Californians took part in an annual earthquake preparedness drill.
A quake with a preliminary magnitude of 3.8 struck about two miles east of Berkeley at 8:16 p.m., the U.S. Geological Survey said.
Thursday night's quake came nearly six hours after a magnitude 4.0 earthquake hit in the same area.
Berkeley police said there were no reports of damage or injuries from either quake.
The second temblor was strong enough to knock photographs off the wall and glasses onto the floor at the home of Diane Coppini, who lives in nearby Emeryville.
"It was a nice jolt," Coppini said in describing the quake.
Despite the timing of the two earthquakes, seismologists could not determine if the second quake was an aftershock to the earlier quake, said USGS geophysicist Shengzao Chen.
The earlier earthquake struck at 2:31 p.m. and was centered across the bay from San Francisco, six miles beneath the University of California, Berkeley, campus, according to U.S. Geological Survey maps.
Jack Boatwright, a seismologist with the USGS, described it as a "sharp little earthquake" that had a "very nice impulsive character."
San Francisco police and officials at UC Berkeley said they had no immediate reports of injuries or damage.
Tami Humphrey, director of a preschool just north of Berkeley, was outside with her students when the quake struck.
"We felt it pretty good. It felt like a drop and then a shake," she said, adding that "the kids didn't even notice."
More than 8.5 million people signed up to participate in the preparedness drill, which took place at 10:20 a.m. and was labeled the Great California ShakeOut.
The quake also came 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.
Seattle resident Joaquin Miller was in Oakland when Thursday's shaking began. He said he first thought it was coming from a passing big rig.
"It wasn't big enough to scare me," the 44-year-old said.
Officials at Bay Area Rapid Transit said the system's trains were delayed about 15 minutes as workers inspected tracks. Officials at Caltrain said none of its trains was delayed.
Associated Press writers Terry Chea, Lisa Leff, Louise Chu and John S. Marshall contributed to his report from San Francisco.