Strong but Strange Earthquake Jars Center of State

A strong, rolling earthquake shook Northern Californians awake early Monday, but after regaining composure they discovered that it had caused no serious injuries and surprisingly little damage.

Worst-hit by the 3:55 a.m. temblor, estimated at 5.3 on the Richter scale, was the James Lick Observatory 50 miles southeast of here and just south of the earthquake’s epicenter near Fremont. A 120-inch telescope at the observatory was disabled.

The sharpest aftershock hit 3.6 on the Richter scale.

The quake hit less than three weeks before the 80th anniversary of the famous earthquake--estimated at 8.3 on the Richter scale--that destroyed this city and killed an estimated 700 to 2,000 people.

The quake was felt by people along a 280-mile stretch of the Central California coastline from Santa Rosa south to San Luis Obispo.

It also sent some tremors through the scientific community, which was puzzled by its unusual nature and location.

Bruce Bolt, director of the seismographic station at the University of California, Berkeley, said the quake occurred somewhere in the San Andreas system, but not on that well-known fault and not in the fashion common to earthquakes in the region.

Interesting Oddity

“One of the interesting things about it is that it doesn’t seem to be located on any known fault in the Mt. Hamilton area,” he said. “When I rushed in here this morning, I would have sworn it was on the Calaveras fault, but it wasn’t. In fact, it wasn’t anything at all like we would have expected from that fault.”

Particularly odd, he said, was that the earth apparently slipped vertically during the quake, not horizontally, as is normal in the San Andreas system.

Bolt added that Monday’s temblor apparently was unrelated to another one, registering 4.0, that shook approximately the same area Saturday morning.

Despite those anomalies, U.S. Geological Survey researchers said the quake is normal in that it fits the pattern of small, strain-relieving temblors that have been recorded in the San Francisco area for almost 30 years.

History Recalled

Robert Wallace, chief scientist at the USGS’s Office of Earthquake Studies, said a similar series of moderately strong quakes were recorded between 1830, when records were first kept, and 1906.

He said those earlier tremors stopped for some period after the devastating Great Earthquake, which flattened San Francisco on April 18, 1906, while temporarily relieving the seismic strain on the San Andreas fault system. The pattern resumed in 1957 with an earthquake in nearby Daly City that registered 5.1 on the Richter scale, Wallace said.

“If the pattern were to follow that (earlier one), there would be perhaps five or six more decades of this kind of (moderate) activity before another major earthquake,” Wallace said. However, he stressed there is no assurance that any pattern is reliable, and repeated the frequent warning that a major quake could occur at any time.

Meanwhile, hospitals Monday reported only a small number of people seeking care for scrapes and bruises after the morning earthquake, including some who cut their feet walking on broken dishes and glassware.

Damage at Observatory

At the Lick Observatory, a UC Santa Cruz facility, Supt. Ron Laub said the quake widened several existing cracks in the building housing the facility’s original 36-inch refractor telescope, and the building was closed.

At the same time, Laub added, the shaking fractured several fittings in the hydraulic system that positions the newer 120-inch telescope. That instrument was left inoperable, he said, and engineers were called in for repairs.

Elsewhere, the damage was less severe. Two wineries near the epicenter, the Weibel Champagne Cellars and Wente Brothers Vineyard, reported no quake damage at all. A liquor store in Fremont reported broken bottles, as did several other stores and supermarkets.

“Mostly, just nuisance things occurred here,” said Earl Thompson, manager of emergency services for the City of Fremont. Most common, he said, were some burglar alarms set off and some small natural-gas leaks.

Commercial nuclear power plants near Sacramento and San Luis Obispo weathered the temblor without incident, said Greg Cook of the federal Nuclear Regulatory Commission’s regional office in Walnut Creek. Indeed, he said a seismograph at the Diablo Canyon nuclear power plant near San Luis Obispo recorded no seismic activity at all in the area.

Pacific Gas & Electric Co. said swaying electrical lines and rattled equipment blacked out nearly 9,300 customers in San Jose and Fremont, but power was restored to most homes by 7:30 a.m.