Quakes Rattle Inland Empire, Bay Area; No Injuries Reported

A moderate earthquake jolted parts of Riverside and San Bernardino counties early Monday, within hours of an unrelated temblor in the San Francisco Bay Area. No damage or injuries were reported.

The Southern California quake, which struck at 8:10 a.m., measured 4.1 on the Richter scale and was centered four miles north of Big Bear Lake. It was felt as far away as Apple Valley in the desert and in San Bernardino, said Kate Hutton of the Caltech Seismological Laboratory.

“We’ve had a lot of calls and alarms, but no damage,” said San Bernardino County Sheriff’s Deputy Duane Lindquist. San Bernardino police, the Riverside County Sheriff’s Department and the state Office of Emergency Services also reported no damage.

The quake, which was not associated with any known fault, occurred in a seismically active “wedge” of ground that slopes beneath the San Bernardino Mountains, said Lucile Jones, a seismologist with the U.S. Geological Survey in Pasadena.

The wedge produces magnitude 4 quakes every couple of years and generated a swarm of them in 1979, Jones said, adding that it starts at the ground surface in the southern Mojave Desert north of Lucerne Valley and slants southward until it reaches a depth of 13 miles near Banning.

Bay Area Quake

An earlier quake struck a wide area of the San Francisco Bay Area late Sunday night, triggering burglar alarms, knocking glasses off shelves and forcing a brief halt in mass transit service.

The University of California seismographic station said Sunday’s temblor struck at 11:45 p.m. and registered 4.3 on the Richter scale. An aftershock of 2.5 magnitude was recorded at 1:43 a.m Monday.

A spokesman said the quake along the Hayward Fault was centered about six miles east of downtown Oakland. Residents of the eastern side of San Francisco Bay said the temblor was felt as a sharp jolt.