A magnitude 3.7 earthquake broke three miles northwest of UCLA at 7:36 p.m. on Sunday, generating shaking that was felt across Los Angeles and Orange counties, says the US Geological Survey. The quake originated just below the earth's surface, which accentuated shaking in some areas. USGS says that the quake occurred northeast of the Newport-Inglewood Rose Canyon fault system, which extends all the way south to San Diego Bay. But it is not clear which fault system produced the quake.

"It wasn't necessarily associated with a named fault," said Susan Hough, a USGS seismologist. "The LA Basin is riddled with small faults."