Southland Rattled by 4.9 Quake Near Big Bear

A magnitude 4.9 earthquake centered north of Big Bear Lake in the San Bernardino Mountains rattled much of urban Southern California, including Los Angeles and San Diego, at 5:08 p.m. Monday, seismologists said.

Car alarms sounded in an area of some cabins about four miles north of Big Bear City, the San Bernardino County Sheriff’s office said, but there were no reports of damage or injuries.

Sheriff’s Sgt. Michael Follett, the watch commander at the department’s Big Bear Lake station, said it “felt like a good one.” He described it as a roller that shook his office for three to four seconds.

Within moments, the station’s switchboard was flooded with calls.

Intensity maps released by the U.S Geological Survey indicated the heaviest shaking, a moderate IV on the Mercalli scale, was actually in a 10-mile oblong southwest of Big Bear. Light shaking occurred roughly from Barstow on the north to Banning on the south.

The Mercalli scale is a description of how an earthquake feels at various spots where it is measured.

The temblor was not considered an aftershock of the 1992 Landers-Big Bear earthquakes, said Lucy Jones, head of the U.S. Geological Survey’s Pasadena office.

Jones said it was centered at a relatively shallow depth of three miles in an area north of the 1992 aftershock zones.

The area has had numerous quakes in the magnitude 4 and 5 range over the years, Jones said, but no really big seismic events.

The quake was felt as a rolling motion in Los Angeles. There was a 3.2 aftershock at 5:42 p.m. and seven smaller aftershocks within two hours.

First reports from Caltech put the quake within a mile of the Helendale fault, but Jones said “there’s a whole welter of faults in the area, and it would be difficult to ascribe this to any particular one.”

Jones said a 4.9 would be too weak to cause any surface rupture, so it would be hard to establish its precise fault zone.