BISHOP — An earthquake measuring 6.1 on the Richter scale hit the Eastern Sierra region at 7:42 a.m. Monday, knocking 53 mobile homes from their foundations in Chalfant Valley, shattering plate-glass windows in downtown Bishop and briefly trapping 300 campers at the Pleasant Valley Reservoir northwest of here.
Only two minor injuries were reported in California's fourth, and strongest, temblor in the past two weeks. Both injuries occurred in Chalfant Valley, a hamlet of 325 residents 11 miles north of Bishop.
A hillside gave way underneath the main access road into the Pleasant Valley campground seven miles outside Bishop, creating a 30-foot-deep hole and damaging a pickup truck without hurting its occupants. Later in the morning, after clearing away boulders, the authorities evacuated the campers by a secondary road.
Power Plants Knocked Out
Fissures, cracks and landslides were reported in other localities. A Sierra Club trail-construction party was briefly stranded by a rock slide that blocked an access road near Pine Lake, 20 miles west of Bishop.
The chief engineer for the Los Angeles Department of Water and Power in the Owens Valley, Duane Buchholz, said three of the agency's power plants, producing a total of 110 megawatts of electricity, were knocked out of service in the Owens River gorge between Bishop and Mammoth Lakes. There was no interruption of power in Los Angeles from the damage.
Seismologists said the quake was on the Owens Valley Fault and was followed by numerous aftershocks, including a 5.2 and a 5.1. The epicenter was 15 miles north of Bishop, between the communities of Chalfant Valley and Hammil Valley, in the same vicinity rattled by a 5.5 temblor Sunday. There had been a number of quakes in the area since July 3, including three magnitude 3 quakes Friday.
Monday's quake was felt over most of California, and in Nevada and Utah as well. Reports of swaying buildings came from as far north as Chico, as far south as Los Angeles and as far east as Salt Lake City. The U.S. Geological Survey in Menlo Park, Calif., said the quake was only about four miles below the earth's surface, which is why it was felt over such a widespread area.
Caltech measured the quake at 6.2 on the Richter scale; the University of California, Berkeley, at 6.1, and the National Earthquake Information Center in Golden, Colo., at 6.0. Such variances are not uncommon when earthquakes are measured from different points and distances.
Seismologists said the Chalfant Valley quake was apparently unrelated to a 5.9 temblor centered near Palm Springs on July 8 and a 5.3 quake off the coast near Oceanside on July 13. A 4.0 aftershock of the Oceanside quake was registered Monday morning, hours after the quake near Bishop.
Altogether, this month has seen the most destructive seismic activity in the state since the May 2, 1983, earthquake that caused widespread damage in Coalinga in the San Joaquin Valley.
The Coalinga quake was a 6.7-magnitude temblor. Each increase of one number on the Richter scale represents a tenfold increase in ground motion.
Although there was no immediate estimate of total damage Monday, the worst destruction was in Chalfant Valley, where, in addition to the 53 mobile homes knocked off their foundations, at least two homes were reported destroyed and almost all of the 145 structures in the community were damaged to some degree.
The town's water supply was disrupted when some pipes burst, and authorities warned residents not to drink the water until silt tests were made. With sewer lines broken, portable latrines were installed.
Victor Benchetler, a building supplier in Chalfant Valley, said he and his wife, Kathy, were asleep when "all of a sudden the whole house felt like it was going to fall down. . . . We ran into the baby's room and grabbed him. Pictures, everything, were falling off the wall. Two console TVs fell over. . . . A chandelier broke off. . . . I've been in rolling quakes, but this was more shaking side to side rather than rolling."
Two Injuries Reported
Kathy Benchetler suffered a few minor cuts, and Dana Sensibaugh, operator of the Chalfant Valley Mercantile store, was struck by falling debris and slightly hurt. They were the only injuries reported in the quake.
Shirley Burnett said she had to claw her way out of her mobile home with a hammer, after the walls collapsed and the structure fell two feet from its foundations, blocking both doors.
Burnett said she was cleaning up the damage in her home from the previous day's quake, when the bigger one hit. She said her first thought was, "Oh my God, there's going to be another mess in my house." A moment later, her only thought was leaving.
"At first, it was a kind of a slow rolling and suddenly it hit hard, and then I said to myself, 'Man, I just better get out of here,' " she said.
Burnett's home appeared to be a total loss.
Becky Manross returned home from her job in Bishop to find a six-foot-deep hole where her previously level front yard had been.