New cluster of minor earthquakes shakes San Ramon area
By Carlos E. Castañeda
Three minor earthquakes struck Friday morning in San Ramon, the latest cluster of quakes to shake the same area in the Tri-Valley region over the last several weeks.
A 3.0 magnitude earthquake struck at 8:14 a.m., followed by a 2.8 and 2.6 magnitude quakes at 8:16 and 8:18 a.m., respectively, according to preliminary data from the U.S. Geological Survey. The quakes were centered in a residential area just south of Bollinger Canyon Drive between Dougherty Road and Alcosta Boulevard.
The area is the same general vicinity where a series of minor quakes have been occurring since November, with the largest being a 4.0 magnitude on December 19, 2025.
None of the earthquakes during this recent swarm has been strong enough to cause significant damage.
San Ramon, which sits atop the Calaveras Fault, has seen similar small quake swarms over the years for reasons that are not fully understood.
“We don’t know exactly why these swarms are occurring exactly where they do,” USGS seismologist and geophysicist Dr. Annemarie Baltay told CBS News Bay Area last month. “But we’ve seen that they can be very focused, and in 1990, we saw one that kind of moved along in time. We think it’s some small, sort of micro-movements along the fault, or along smaller faults in the area. And that’s just generating a couple of little earthquakes that just pop off and trigger each other.”
This is a breaking news update. More information to be added as available.
