Magnitude-4.6 earthquake shook Southern California.

The quake struck northwest of Malibu in the Santa Monica Mountains.

More than a dozen aftershocks were reported, with the largest of magnitudes 3.0 and 2.7.

Shaking felt by up to 12 million people across Los Angeles area.

Even areas in north San Diego County experienced weak shaking.

No significant damage reported, Los Angeles Fire Department conducts survey.

Possibly occurred on Malibu Coast Fault near populous areas like Pacific Palisades and Santa Monica.

Coincides with anniversary of 1971 San Fernando earthquake.

Unrelated quake on Hawaii's Big Island also occurred, no tsunami warning issued.