A series of mostly smaller quakes that awakened San Ramon residents on Monday continued to rattle the area by late morning.
Monday’s quake swarm began with a 3.8 shaker at 6:27 a.m. Since then, two dozen quakes above 2.5 magnitude have been recorded in the area — the largest a 4.2 jolt just after 7 a.m., according to the U.S. Geological Survey.
Another 22 quakes below 2.5 have also been recorded in the area on Monday morning, the USGS said.
The quakes are centered near the northern section of the Calaveras Fault.
The temblors were felt in nearby cities, including Dublin, Danville and Pleasanton. There were no immediate reports of injuries or significant damage.
A number of small earthquakes of 4.0 or lower have been recorded since early November 2025 in the San Ramon area.