Another aftershock with a 2.5 magnitude struck Saturday morning, after two small quakes shook the East Bay the day before, according to the U.S. Geological Survey.
The temblor shook 2 miles east-southeast of Berkeley at 12:45 a.m. with a 4.9 depth, according to the survey.
Last Friday, a 2.8-magnitude quake struck at 12:06 a.m. and was followed by a 1.3-magnitude quake minutes later at 12:14 a.m.
These aftershocks follow an earthquake Thursday at 2:41 p.m.,
which was recorded at 4.0 magnitude. A small 3.8-magnitude quake followed Thursday evening at 8:16 p.m., the USGS said.
These earthquakes have been centered around Berkeley.
Thursday's earthquake was along the Hayward Fault Line, according to the USGS.
The U.S. Geological Survey has downgraded Thursday night's earthquake from its original preliminary magnitude of 4.2, to 3.9 a short time later, and now experts report it was a 3.8-magnitude tremor.
The quake struck at 8:16 p.m. and was centered about one mile east of Berkley with a depth of 6 miles, the USGS said.
BART officials stopped all trains when the quake occurred and began track inspection. No injuries or damage was reported, according to BART spokesman Jim Allison.
The temblor created a large jolt in San Francisco, including the Civic Center area, Nob Hill, Richmond District, and Haight-Ashbury neighborhood, and was felt throughout the region including Danville, Santa Cruz, Palo Alto, Oakland and Berkeley.
A 4.0-magnitude earthquake struck the area at 2:41 p.m. Thursday. That quake was centered about two miles east-southeast of Berkeley, and had a depth of 6.1 miles, according to the USGS.
After Thursday's first quake, Keith Knudsen, deputy director of the USGS Earthquake Science Center in Menlo Park, said it was a standard Hayward Fault Line quake.
He said the temblor was of the typical "strike-slip" variety, in which two sides of the fault slide horizontally, he said.
Thursday's earthquakes occurred on the same day as the Great California ShakeOut, a statewide drill in which millions of Californians practiced ducking and covering at 10:20 a.m.