3.8-magnitude quake rattles San Francisco Bay Area, geologists report

A 3.8-magnitude earthquake shook Concord near San Francisco on Thursday morning, the U.S. Geological Survey reports.

The 4-mile-deep quake hit a mile west of Concord at 11:18 a.m. Pacific time, according to the USGS. Dozens of people from as far away as Point Reyes reported feeling the tremor.

No injuries or damage were initially reported.

“Well this literally shook up my math lesson!” wrote a teacher on Twitter. “I didn’t feel it since I don’t live close to Concord but my kids started unmuting and yelling that there was an earthquake. They all live in Walnut Creek! Talk about a lively lesson!!”

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.