Moderate Quake Jars Sierra, San Joaquin Valley

A rolling earthquake shook the Sierra Nevada and a 200-mile stretch of the San Joaquin Valley early Sunday, tossing merchandise off shelves, toppling boulders onto dirt roads and knocking out power to 5,000 residents, authorities said.

There were no reports of injuries or significant damage from the third widely felt temblor to strike California in a two-week span, police said. Sunday’s quake was centered in the eastern Sierra about 15 miles north of here.

The 7:30 a.m. quake was estimated at 5.5 on the Richter scale, a magnitude of moderate intensity, said seismologist Kate Hutton at Caltech.

The U.S. Geological Survey in Washington also registered the temblor at 5.5, while the University of California, Berkeley, said it measured 5.6 and the state Department of Emergency Services had still another reading, 4.7.

The epicenter placed the quake four miles below the earth’s surface and three miles east of the tiny town of Chalfant Valley in a sparsely populated area near Crowley Lake in Mono County.

About three-quarters of the 5,000 residents of Bishop lost power after the quake, police dispatcher Dick Bales said. The temblor knocked out power transformers briefly, but electricity was restored within an hour.

“It was a pretty good one,” Bales said. “No one has been hurt and we haven’t had any damage reported, just some stuff knocked off store shelves.”

A woman who works at the Mini-Mart in Chalfant Valley, the only store in the hamlet, had the same problem. “All materials that were on the shelf are now on the floor,” she said.

The quake was felt for hundreds of miles in the San Joaquin Valley, from Bakersfield to Fresno to Modesto. The largest of a series of 200 aftershocks was estimated at 3.4 at 8:29 a.m., said Brian Miller, a U.S. Forest Service spokesman.

The eastern Sierra is one of the most geologically active areas of the state. Mammoth Lakes, 40 miles northwest of Bishop, sits atop an ancient volcanic caldera. The area’s faults have generated several quakes since 1980, the largest a 5.7 temblor in November, 1984.

Sunday’s quake apparently occurred on a fault running along the White Mountains, Miller said. Some dirt roads were closed by fallen rocks, but main routes were not affected. Volunteer fire departments throughout the area were activated and crews were checking for injuries or damage at campgrounds.

Hutton said the quake was not related to two moderate quakes that struck Southern California earlier this month. On July 13, a 5.3 quake centered in the ocean off Oceanside shook a wide area of Southern California. On July 8, a 5.9 jolted the desert north of Palm Springs, causing $6 million in damage to homes, roads and utilities.