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M4.2 earthquake near San Ramon caps four-day sequence on Pleasanton fault

An M4.2 earthquake struck 4 km southeast of San Ramon, California on February 2, 2026 at 7:01 AM PST (15:01:13 UTC). USGS placed the epicenter in Contra Costa County at a depth of 9.6 kilometers, about 0.2 km from the mapped trace of the Pleasanton fault. The event was the largest in a sequence of seven earthquakes M3.1–M4.2 at the same epicenter between January 30 and March 2.

The main shock drew 5,030 "Did You Feel It?" reports submitted to USGS, with a community-reported intensity (CDI) of 4.6 and ShakeMap's modeled maximum instrumental intensity (MMI) of 5.2. Both values are consistent with light-to-moderate shaking felt across the East Bay.

USGS PAGER estimated about 4.19 million people were within range of light shaking (MMI ≥3), with about 103,700 experiencing moderate shaking (MMI ≥5). PAGER issued a green alert, meaning no significant damage or casualties are expected. USGS assigned the main shock a significance score of 729 on its internal 0–1000 scale.

The sequence began with an M3.4 foreshock on January 30 (640 felt reports). On February 2, an M3.8 (1,500 reports) and an M3.1 struck within three minutes of each other, followed thirty-two minutes later by the M4.2 main shock. An M3.8 aftershock followed twenty-six minutes after, and an M3.2 the next day. A late M3.2 aftershock occurred on March 2 — twenty-eight days after the main shock, at the same epicenter.

USGS catalog data shows one other M4.2+ earthquake within 20 km of this epicenter in the past 10 years, suggesting events of this size occur about once every 10 years at this location.

Contra Costa County has a population of approximately 1,087,000.

Event data

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