Another swarm of earthquakes centered in San Ramon shook the East Bay on Monday morning, including a 4.2 magnitude quake felt across a wide swath of the Bay Area, authorities said.
The U.S. Geological Survey said the first earthquake, measuring a 3.8 magnitude, struck just before 6:30 a.m. in the area just south of Bollinger Canyon Road between Alcosta Boulevard and Dougherty Road. At least 20 additional earthquakes of at least a 2.5 magnitude struck that same general area over the next several hours.
The 4.2 quake hit at 7:01 a.m. and was centered at the southern end of the Canyon Lakes Golf Course, according to the USGS.
U.S. Geological Survey
It is the same area where multiple swarms of minor quakes have struck since November 2025 and have been felt across the Tri-Valley, with the largest being a 4.0 magnitude shaker on December 19. San Ramon, which sits atop the Calaveras Fault, has seen other small quake clusters over the years for reasons that are not fully understood.
No significant damage was reported on Monday, but residents and some businesses reported items falling off shelves.
BART trains were running at reduced speeds following the quakes as the agency worked to complete track safety inspections.
Cecilio Padilla
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