San Ramon Rattled by 3.3 Magnitude Earthquake

A magnitude 3.3 earthquake struck San Ramon late Sunday night, March 1, 2026, followed by a series of smaller quakes.

According to the U.S. Geological Survey (USGS), the quake occurred at 11:21 p.m. PT at a depth of 8.4 kilometers along the Calaveras Fault. The epicenter was located just southwest of San Ramon. No injuries or structural damage were immediately reported.

As of Monday morning, no “Did You Feel It?” reports had been submitted to the USGS. Light shaking was reported in nearby communities including Dublin, Blackhawk, and Diablo.

The magnitude 3.3 quake was followed by several smaller earthquakes in the same region. A magnitude 2.8 quake was recorded at 12:33 a.m. PT. Additional quakes ranging from magnitude 1.5 to 2.3 were recorded between 11:24 p.m. and 12:47 a.m., including magnitudes 2.3, 2.0, 1.8, and 1.5. All were centered southeast of San Ramon.

Such clusters are often described as earthquake swarms, which are a series of small earthquakes occurring in the same area without a single, clearly defined mainshock. Swarms can last minutes, hours, or even days as stress adjusts along a fault.

The quakes were linked to the Calaveras Fault, a right-lateral strike-slip fault that is part of the Bay Area’s fault system, according to the USGS. In a strike-slip fault, the two sides move horizontally past each other. The fault is divided into segments that behave differently.

Some sections move slowly and steadily, shifting only a few millimeters per year or about 2 millimeters annually in northern sections and up to 14 millimeters along parts of the central segment. Other sections are more locked, allowing stress to build over time before being released in a larger earthquake.

On February 2, 2026, a magnitude 4.2 earthquake struck near San Ramon, triggering a swarm that was felt across parts of the Bay Area, according to USGS data.

Small earthquakes are common in active fault zones and often reflect ongoing adjustments within the Earth’s crust.

USGS officials urge residents to remain prepared. Before an earthquake, people are advised to secure heavy furniture, develop a family communication plan, assemble emergency supplies, protect important documents, and review insurance coverage.

During shaking, the USGS recommends people “Drop, Cover, and Hold On,” staying indoors and away from windows. After a quake, residents should check for injuries, hazards, and possible aftershocks.

The Bay Area lies within one of the most seismically active regions in the United States, where ongoing fault movement is constant.