The U.S. Geological Survey (USGS) reports the earthquake was not serious but a routine occurrence in an area well known for quakes.
The Mercury News reports the earthquake took place near the Calaveras Reservoir 11 miles from San Jose City Hall. There was no apparent damage and no one was injured.
"Usually you just hear a ripple of the roof,'' park ranger Neil Spargur from the nearby Sunol Regional Wilderness park told Mercury News adding, "This one we felt in the entire building."
USGS seismologist David Oppenheimer, speaking to Mercury News, said, "In the big picture, doesn't mean anything. It's just part of the natural background process" along this agitated section of the fault, which routinely releases stress.
The earthquake was felt in San Francisco, and at least as far north as San Ramon. People who reported their experience with the quake on the USGS website were mainly residents of Milpitas, Fremont, Pleasanton and Livermore areas.
"The mirror on my dresser was going back and forth and it rumbled," Marilyn Holliday told Mercury News. She was at home in the Mission Valley area of Fremont at the time.
There is an old dam at Calaveras Reservoir which as it only holds low levels of water is relatively safe from earthquakes. The dam is scheduled to be replaced due to concerns about what would happen during a major earthquake.