San Ramon, CA – Residents across the East Bay felt shaking Sunday afternoon after two earthquakes struck just southeast of San San Ramon, CA – A growing earthquake swarm intensified Monday morning after a magnitude 4.2 earthquake — the strongest so far — struck southeast of San Ramon, according to the U.S. Geological Survey.
According to the USGS, the magnitude 4.2 earthquake hit at 7:01 a.m. Monday, centered about 4 kilometers east-southeast of San Ramon, at a depth of approximately 9.0 kilometers. The quake was widely felt across Contra Costa County and parts of the East Bay, prompting a surge of shaking reports.
The latest quake followed multiple earlier earthquakes in the same area, now officially classifying the activity as an earthquake swarm. Earlier Sunday, a magnitude 3.9 earthquake struck at 6:27 a.m., followed minutes later by a magnitude 3.3 event. Two additional magnitude 2.5 earthquakes were recorded at 6:48 a.m. and 6:56 a.m., all within a few kilometers of each other.
Residents in San Ramon, Danville, Dublin, Pleasanton, and nearby East Bay communities reported stronger shaking with the 4.2 quake, including rattling windows, swaying light fixtures, and brief but noticeable movement. USGS “Did You Feel It?” data indicates light to moderate shaking, stronger than earlier events in the swarm.
Seismologists describe earthquake swarms as clusters of related earthquakes without a single clear mainshock, though the magnitude 4.2 is now the dominant event in this sequence. Experts stress that while swarms can continue for hours or days, they do not automatically signal a larger earthquake, though aftershocks remain possible.
As of Sunday morning, no injuries or damage have been reported. Emergency officials encourage residents to remain prepared and to report shaking through the USGS “Did You Feel It?” system to aid real-time analysis.
This article was produced by a journalist and may include AI-assisted input. All content is reviewed for accuracy and fairness.
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