A cluster of earthquakes in the San Francisco Bay Area early Monday including a magnitude 4.2 temblor was felt by thousands.
The United States Geological Survey reported more than two dozen different quakes. The largest was a M4.2 east of San Ramon at a depth of 5.8 miles on the Calaveras Fault, a right-lateral, strike-slip fault
There were no immediate reports of damage or injuries.
Operators of the area’s rail line, BART, issued an alert advising passengers that trains were running at reduced speeds as crews undertook track safety inspections as a result of the quake, the San Francisco Chronicle reported.
The USGS told ABC7 Eyewitness News in an interview the cluster is a continuation of the swarm of quakes the area has been experiencing. The area had its first earthquake in weeks on Friday, however there have been dozens of quakes since November.
The southern half of the central segment of the Calaveras Fault has historically been the most seismically active segment of the fault. It produced the M6.2 Morgan Hill earthquake in 1984 and a M6.2 earthquake in 1911, according to the USGS.
A working group in 2003 assigned an 11% probability that the Calaveras Fault would produce a magnitude 6.7 or larger earthquake in the next 30 years.
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