A magnitude 5.1 earthquake rattled the San Francisco Bay Area on Tuesday, causing delays of some commuter trains. There were no immediate reports of damage or injuries. The US Geological Survey said the 11:42am quake was centered 12 miles east of San Jose at a depth of about 4 miles. The area is hill country about 40 miles southeast of downtown San Francisco. Lucy Jones, a veteran California seismologist, told NBC Bay Area 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
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, the AP reports. "We had a frame in the house fall, everything was shaking but once it stopped, there was no damage," he said. 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 USGS.