SAN RAMON, CA — A magnitude 4.2 earthquake struck south of San Ramon on Monday morning. It was the strongest in a series of tremors that rattled the San Francisco Bay Area and delayed commuters.
According to the U.S. Geological Survey (USGS), the quake hit shortly after 7:00 a.m. on Feb. 2. The event was part of a cluster of more than a dozen minor tremors recorded in the San Ramon area between 6:30 a.m. and 7:30 a.m.
Earthquake experts identified Monday’s activity as an "earthquake swarm." This happens when several quakes strike one area without the usual pattern of a single large earthquake followed by aftershocks. Experts noted that these swarms are common in San Ramon, a region known for frequent, small earthquakes.
Although the earthquake was centered south of San Ramon, residents more than 30 miles away felt the shaking. People in San Francisco and East Bay cities like Oakland and Richmond reported feeling the ground move. Early reports showed no major damage in the area, despite the widespread shaking.
The tremors disrupted travel throughout the region on Monday morning. Bay Area Rapid Transit (BART) warned passengers of potential delays after officials slowed trains to inspect the tracks for damage. BART resumed normal speeds after the safety checks.
The quakes follow a busy period for the area. The San Francisco Chronicle reported that USGS data showed 87 earthquakes of magnitude 2.0 or higher in Contra Costa County during November and December 2025.
