A second earthquake of 3.8 magnitude hit the Hayward fault near Berkeley, Calif., at 08:16:05 p.m. Pacific Time Thursday.
According to the U.S. Geological Survey, the second quake came nearly six hours after a 4.0 magnitude earthquake jolted the same area.
The quake was centered one mile east from Berkeley. The quake was felt throughout the East Bay and San Francisco.
No damage or injuries were reported from either earthquake, Berkeley police said.
Bay Area Rapid Transit officials said the trains were experiencing minor delays because of routine checks after an earthquake.
The first quake struck at 2:31 p.m. and was centered across the bay from San Francisco and the second was about 9.6 kilometers (six miles) deep, according to the USGS.
“The second quake was a little stronger because the epicenter was six miles deep. The path is very simple from a deeper quake and this simple path was felt very abruptly and very sharply, and that's why people felt it so strongly, said Jack Boatwright, a USGS seismologist.
The quake on Thursday came almost 22 years to the day after the Loma Prieta earthquake struck the Bay Area in 1989 during the World Series. The 6.9 magnitude earthquake in 1989 killed 63 people; around 3,800 were injured and caused a damage of $10 billion.
The quake also came on the day Californians participated in an annual earthquake preparedness drill at 10:20 a.m. Thursday. More than 8.5 million people signed up to participate in the 2011 Great California ShakeOut.