3.1-magnitude quake jolts San Francisco Bay Area in California, seismologists say

A 3.1-magnitude earthquake shook the San Francisco Bay Area in California, the U.S. Geological Survey reported.

The nearly 9-mile-deep quake hit about 20 miles from Portola Valley at 9:28 p.m. Wednesday, July 30, according to the USGS.

More than 200 people from as far away as Fresno and El Cerrito reported feeling the earthquake to the agency.

Portola Valley 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 July 31, 2025 at 9:28 AM with the headline "3.1-magnitude quake jolts San Francisco Bay Area in California, seismologists say."