Magnitude 5.1 quake strikes near San Jose

Lucy Jones, a veteran California seismologist, told KNTV-TV that the quake happened on the Calaveras fault, one of eight major faults in the Bay Area.

"The Calaveras fault is one that tends to have smaller earthquakes," Jones said.

It was the largest earthquake in the Bay Area since a magnitude 6.0 jolt in the Napa wine country in 2014, Jones said in a social media post.

The 138-mile long Calaveras fault is a major branch of the San Andreas fault and runs from San Juan Bautista in the south to San Ramon in the north, Jones said.

Rich Constantine, the mayor of Morgan Hill, a city next to San Jose, said he was in the kitchen of his home when the "long and steady" quake struck.

"We had a frame in the house fall, everything was shaking but once it stopped, there was no damage," he said.

Constantine said Morgan Hill's City Hall and other city offices were evacuated but that everyone returned to work soon after.

People reported feeling the quake as far south as the scenic Big Sur coast, 75 miles south of the epicenter in the region of Joseph Grant Ranch County Park, a huge natural area.

A 3.1 aftershock followed about 5 minutes later, according to the U.S. Geological Survey.

Several commuter train companies, including Cal Train and the Bay Area Rapid Transit system, known as BART, held trains to check for damage. BART returned to normal service by early afternoon.