The San Ramon Valley experienced more than 20 earthquakes since Friday morning, the latest in a string of hundreds of small quakes in the area, according to the U.S. Geological Survey officials.
Researchers at the USGS expect this quake storm to continue for another few weeks, but there are no predictions of it leading to major seismic activity.
The largest temblors during the past three days were a preliminary 3.2 on Friday at 6:48 a.m., a preliminary 3.1 at 12:43 a.m. Saturday, a preliminary 3.2 seconds later at 12:44 a.m. Saturday and a preliminary 2.7 at 11:26 p.m. Saturday, according to the USGS.
In all, more than 240 quakes have struck the San Ramon area in the last week. The largest was a preliminary 3.6 quake that struck last Monday.
Friday morning's quake occurred along the Calaveras Fault, which intersects with the Hayward Fault, a member of the San Andreas Fault system, according to the USGS and the University of California at Berkeley Seismological Laboratory.
A USGS geophysicist said the swarm of quakes does not necessarily mean a damaging quake will occur anytime soon.
"We've had swarms like this (in this area) in the past and none have led to a large, damaging earthquake," USGS research geophysicist Brad Aagaard said earlier this week.
The Working Group on California Earthquake Probabilities, which builds forecasts of earthquakes, said there is an 11% chance the Calaveras Fault will produce a 6.7-magnitude earthquake or larger in the next 30 years, according to the USGS.
Aagaard said USGS officials expect the swarm of earthquakes in the San Ramon area to last for about two more weeks.