Magnitude 4.2 Earthquake Shakes Bay Area
A 4.2 magnitude earthquake struck the San Francisco Bay Area early on February 12, causing minor shaking and disruptions. No major damage or injuries were reported, but the event prompted local authorities to advise residents to review their earthquake preparedness plans.
- The 4.2 magnitude earthquake struck at 7:01 a.m. on Monday, February 2, 2026, with its epicenter located about 2.5 miles southeast of San Ramon. - This event was part of an "energetic" earthquake swarm that included over 20 temblors in the same area on the same day, with a magnitude 3.8 quake preceding the main shock just before 6:30 a.m. - The seismic activity is centered in the Tri-Valley region, an area known for such swarms due to a complex web of smaller subfaults related to the Calaveras Fault, Mount Diablo Thrust Fault, and the Concord-Green Valley Fault system. - San Ramon has a history of similar seismic events, with earthquake swarms also occurring in 1970, 1990, 2003, and 2015, among other years. - While no major damage was reported, the quakes prompted Bay Area Rapid Transit (BART) to run trains at reduced speeds for safety inspections, causing system-wide delays of up to 20 minutes. - According to the U.S. Geological Survey (USGS), the probability of a larger earthquake resulting from this swarm remains low, with a 3% risk of a quake magnitude 4.0 or higher. - Seismologists note that while swarms on the Calaveras Fault are common, there is a 72 percent probability of at least one earthquake of magnitude 6.7 or greater striking the wider Bay Area on a major fault like the Hayward or San Andreas before 2043.
