According to the USGS, an earthquake happens due to sudden movements of tectonic plates along fault lines that separate them.

N​early 75% of the country is at risk for a potentially damaging earthquake, according to a recently updated USGS map.

(FOX40.COM) — On Thursday night, three earthquakes were detected near California’s most active fault, the San Andreas Fault, ...

The preliminary measurement from the USGS was a 3.7 ... struck on the San Andreas Fault, which runs from the Cape Mendocino region north of the Bay Area to Baja California, Mexico.

The USGS says it was about three miles from the San Francisco Zoo near the San Andreas Fault and the depth of ... size happen more often than we think. California has around 50 a day.