Mild late-night earthquake stirs up San Francisco Bay Area, seismologists say

A 2.9-magnitude earthquake shook the Northern California coast near San Francisco overnight, the U.S. Geological Survey reports.

The 6-mile deep quake hit near Piedmont at 10:31 p.m. on Sunday, Sept. 11, according to the USGS.

More than 4,400 people from as far away as Sacramento and Fresno reported feeling the tremor to the agency.

The quake hit about 2 miles north of Piedmont, a city of 11,000 people about 15 miles east of San Francisco.

“Earthquake! A little one. Quick shake of the house,” read one Twitter post.

“WHOA did anyone else feel an earthquake just now in San Francisco?” asked another.

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.