HOLLISTER, CA — An earthquake swarm that struck central California this week has scientists keeping an eye on the well-known San Andreas Fault.

According to data supplied by the U.S. Geological Survey in Menlo Park, an earthquake swarm struck the area near Ridgemark — just south of Hollister — Sunday night into Monday morning, when 18 earthquakes of varying intensities struck within a 24-hour period.

It's been a common occurrence lately.



On Tuesday afternoon, a magnitude 4.2 quake struck the area at 2:38 p.m. That night, another temblor hit, when a 3.0 quake was reported, south-southeast of Ridgemark, at 10:14 p.m., according to the USGS. The quake was felt as far away as Atascadero to the south.



The area lies directly over the San Andreas Fault. The Oct. 17, 1989 Loma Prieta earthquake is the most recent major earthquake associated with the San Andreas Fault. The 7.9 magnitude 1906 San Francisco earthquake was the largest earthquake ever recorded on the fault, according to the USGS.

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