Swarm of more than 20 quakes shakes San Francisco Bay Area, seismologists say

A swarm of more than 20 earthquakes reaching up to 3.8 magnitude rattled San Ramon near San Francisco in Northern California, the U.S. Geological Survey reports.

The other quakes in the Sunday, Nov. 9, swarm ranged from 1.0 to 3.7 magnitude as of 11 a.m., according to the USGS.

The series of quakes, including the 3.8 temblor, began at 9:38 a.m., the USGS reported.

More than 1,300 people from as far away as Mill Valley and Half Moon Bay had reported feeling the 3.8-magnitude quake to the agency as of 11 a.m.

San Ramon is about a 35-mile drive southeast from San Francisco.

What to know about earthquakes

Magnitude measures the energy released at the source of the earthquake, the U.S. Geological Survey says. It replaces the old Richter scale.

Quakes between 2.5 and 5.4 magnitude are often felt but rarely cause much damage, according to Michigan Tech. Quakes below 2.5 magnitude are seldom felt by most people.

Earthquakes’ sudden, rapid shaking can cause fires, tsunamis, landslides or avalanches. They can happen anywhere, but they’re most common in Alaska, California, Hawaii, Oregon, Puerto Rico and Washington, according to the Department of Homeland Security.

If an earthquake strikes, it’s best to protect yourself right away. Here are tips from experts:

• If you’re in a car: Pull over and stop. Set your parking brake.
• If you’re in bed: Turn face-down and cover your head with a pillow.
• If you’re outdoors: Stay away from buildings. Don’t go inside.
• If you’re inside: Stay and don’t run outdoors. Stay away from doorways.

The best way to protect yourself during an earthquake is to drop, cover and hold on, officials say.

“Wherever you are, drop down to your hands and knees and hold onto something sturdy,” officials say. “If you’re using a wheelchair or walker with a seat, make sure your wheels are locked and remain seated until the shaking stops.”

Be sure to cover your head and neck with your arms, and crawl under a sturdy table if possible. If no shelter is available, crawl to an interior wall away from windows.

Once under a table, officials say you should hold on with one hand and be ready to move with it.

“There can be serious hazards after an earthquake, such as damage to the building, leaking gas and water lines, or downed power lines,” officials say. “Expect aftershocks to follow the main shock of an earthquake. Be ready to Drop, Cover, and Hold On if you feel an aftershock.”

This story was originally published November 9, 2025 at 11:16 AM with the headline "Swarm of more than 20 quakes shakes San Francisco Bay Area, seismologists say."