The USGS reports a magnitude 3.2 earthquake struck near San Ramon just after 7:30 a.m. Thursday as part of a cluster of 83 quakes within about a one-mile radius since Nov. 9. The tremors range from magnitude 0.6 to 3.8 and occur roughly 3 to 6 miles deep along the Calaveras Fault. Scientists classify the activity as an earthquake swarm and say the pattern and depths do not indicate a larger quake is imminent. The San Ramon–Danville corridor has experienced similar swarms in the past, including a major episode in 2015.
3.2-Magnitude Quake Jolts San Ramon — Part of Ongoing Swarm on the Calaveras Fault
The USGS reports a magnitude 3.2 earthquake struck near San Ramon just after 7:30 a.m. Thursday as part of a cluster of 83 quakes within about a one-mile radius since Nov. 9. The tremors range from magnitude 0.6 to 3.8 and occur roughly 3 to 6 miles deep along the Calaveras Fault. Scientists classify the activity as an earthquake swarm and say the pattern and depths do not indicate a larger quake is imminent. The San Ramon–Danville corridor has experienced similar swarms in the past, including a major episode in 2015.
02:20 AM, 11/21/2025Science
A magnitude 3.2 earthquake shook the San Ramon area just after 7:30 a.m. Thursday, the U.S. Geological Survey (USGS) reported. The event is part of a concentrated cluster of seismic activity in the San Ramon Valley that has recorded dozens of small quakes in recent weeks.
Overview
USGS data show the San Ramon Valley has experienced 83 recorded earthquakes since Nov. 9, concentrated within roughly a one-mile radius. Reported magnitudes in the cluster range from about 0.6 up to 3.8. Most of the events are too small to be felt, though the stronger ones have produced noticeable shaking for local residents.
What we know
Location and fault: Preliminary analysis indicates the sequence is occurring on the Calaveras Fault, a highly active branch of the broader San Andreas Fault system. This segment runs beneath parts of the East Bay, including San Ramon, Danville, Dublin and Pleasanton.
Type and depth: The recorded events appear to be strike-slip quakes—where two sides of a fault slide horizontally past one another. USGS locates these earthquakes at depths of roughly 3 to 6 miles beneath the surface. One of the larger events in the series reached magnitude 3.8 at an estimated depth near 5.7 miles.
Seismologists' assessment: Scientists characterize the sequence as an earthquake swarm—a burst of many small quakes over a short period—rather than a single mainshock followed by classic aftershocks. Based on depth and the pattern of events so far, seismologists say there is no clear evidence that a larger, damaging earthquake is imminent.
Historical context
The San Ramon–Danville corridor has a history of similar swarm activity. Notably, in 2015 more than 400 small quakes occurred over about five weeks, one of the most active swarm episodes recorded in the Bay Area. Earlier swarms were recorded in 1990 and periodically through the 2000s and 2010s. Experts note that the Calaveras Fault system commonly releases built-up stress through frequent, smaller adjustments.
What residents should do
While seismologists do not expect a larger quake based on current data, residents should remain prepared: secure heavy furniture and objects, review "Drop, Cover, and Hold On" earthquake procedures, keep an emergency kit stocked, and monitor official USGS updates and local emergency alerts.
Source: U.S. Geological Survey