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yesterday

Rapid Earthquake Swarm Rattles San Ramon With Two Magnitude 4.0 Quakes

Seismologists describe the bursts as recurring Calaveras Fault swarm behavior rather than a signal of an imminent large quake.

People living in San Ramon and its hills, seen here in April 2013, have been rattled by dozens of small earthquakes in the last few months.
California earthquake today: Tremors felt in Bay Area, San Ramon, Hayward, Dublin, and Pleasanton
Two people cool off in the waters of Alameda Beach in Alameda, California, Wednesday, Oct. 2, 2024 during a heat wave across the Bay Area and inland.
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Overview

  • USGS data show a roughly 30-minute sequence Friday evening produced multiple quakes from magnitude 2.5 to 4.0 a few miles southeast of San Ramon.
  • BART temporarily ran trains at reduced speeds for track inspections and later warned of residual delays after completing checks.
  • No injuries or structural damage had been reported as of late Friday, and no tsunami warnings were issued.
  • Researchers attribute the activity to the Calaveras Fault’s complex branching and possible fluid movement, which has also driven past Tri‑Valley swarms.
  • USGS notes about a 5 percent short‑term chance of a larger event after a moderate quake, while longer‑term Bay Area odds for magnitude 6.7 or greater are estimated at 72 percent by 2043.