San Ramon Hit By Quakes For Third Time In Under 24 Hours

SAN RAMON, CA — Three earthquakes hit San Ramon Saturday night, the third round in less than 24 hours.

The first was a 3.9 that struck at 6:31 p.m. Saturday, followed by a 2.8 at 6:36 p.m. and a 3.0 at 6:53 p.m., according to the United States Geological Survey. Residents reported feeling the 3.9 weakly around the East Bay and in some spots in San Francisco and the Peninsula.

The latest swarm is the second batch of earthquakes to hit San Ramon on Saturday, and the third to hit in under 24 hours. On Friday night from 7:41 to 7:57 p.m., five earthquakes struck, which ranged from a 2.5 to a 3.8. The following morning at 8:10, a 2.6 magnitude earthquake hit the city.

Swarms also hit last Monday and Tuesday, the continuation of an unusually active stretch of seismic activity.

In the past month alone, San Ramon has seen nearly 150 earthquakes, its second highest number in nearly 50 years, according to the San Francisco Chronicle.
The city sits along the Calaveras Fault, and several micro-faults along the main fault result in swarms of quakes. When fluids like water or gas move through a complex web of cracks in tiny faults, this can trigger many dozens of small quakes in quick succession.

SEE ALSO:

• Earthquake Strikes San Ramon Saturday Morning
• Earthquake Swarm Rattles San Ramon For The Third Time This Week
• Why Does San Ramon Get So Many Earthquakes?
• 5 Things Most People Don't Know About Earthquakes
• Earthquake Swarm Rattles Bay Area Overnight. USGS Weighs Chances Of Bigger Ones To Come
• Morning Quake Rattles The East Bay