The biggest quake was a notable 4.2-magnitude shaker just after 7 a.m. amid an hour-long swarm that began with a 3.9-magnitude earthquake at 6:30 a.m., according to USGS data.

Thousands of people felt the moderate shaking across the Bay Area, according to USGS’s “Did You It Feel It?” survey.

No injuries or property damage have been reported, according to KTVU.

At least 19 earthquakes have been confirmed Monday as well as other smaller aftershocks.

San Ramon, located along the Calaveras Fault, has been a recent hotbed of geological activity, with more than 300 earthquakes reported there since Dec. 1, 2025, KTVU reported.

Two earthquakes were recorded on Friday and another in nearby Dublin, according to the USGS.

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The Calaveras Fault, known as a creeping fault, moves slowly and stress is released in spates of small-to-moderate earthquakes.

Sometimes, enough stress is released for a 4.0 magnitude earthquake.

San Francisco Bay Area Rapid Transit District [BART]  trains are running at reduced speeds while track inspections are completed, causing delays for the Monday morning commute, KRON reported.

Sometimes, enough stress is released for a 4.0 magnitude earthquake.

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