Skyscrapers Sway as Sharp Quake Jolts S.F. Bay Area

Skyscrapers swayed and groceries tumbled from supermarket shelves but no serious injuries or damage were reported Monday when a sharp earthquake along the San Andreas fault jolted the San Francisco Bay Area.

Loma Prieta, a ridge in the Santa Cruz Mountains between San Jose and the coast, was cited as the epicenter of the tremor, the third moderate quake to rattle California this month.

Scientists, however, could not agree on the precise strength of the latest temblor, which shook a 170-mile stretch from Monterey to Santa Rosa. The U.S. Geological Survey in Menlo Park and the National Earthquake Center in Golden, Colo., rated it at 5.0 while the seismographic stations of UC Berkeley calculated it at 5.7.

Earthquakes rated 5.0 or higher are considered capable of causing moderate damage, but the nature of the scale means a 6.0 earthquake would release 30 times the energy of a 5.0 temblor.

Possible Explanation

Berkeley staff research associate Rick McKenzie said a number of reasons, such as the way in which seismic waves move through different rock formations, could account for the different readings.

Whatever its magnitude, the earthquake, which hit at 11:43 a.m., shook people as well as buildings.

“We felt a pretty good jolt--a couple of them, in fact,” said Pat Meyer of the Paul Masson Winery in Saratoga. The winery building itself, and others in the area, escaped serious damage.

Ceiling tiles fell atop shoes shaken from their shelves at a store in San Jose and a rockslide temporarily blocked a mountain road in Scotts Valley north of Santa Cruz.

“Every aisle was messed up,” said Celia Kettle, a supermarket clerk in southeast San Jose. “The cleanup took more than an hour. There were a lot of broken bottles.”

Rides at the Great America amusement park in Santa Clara were closed for 15 minutes and inspected before reopening, but many of the roller-coaster patrons were left wondering why.

“If you were already in motion, there would be no real way that you would notice it,” said spokeswoman Lise Shannon.

Commuter and subway trains throughout the Bay Area also were briefly halted while their tracks were inspected, but were soon returned to service.

In San Francisco, the seismic wave shook skyscrapers and jiggled City Hall. Securities traders at one Financial District high-rise reportedly began betting on the earthquake’s magnitude as soon as the swaying stopped.

A state Supreme Court clerk in San Francisco received some advance warning when a colleague in San Jose interrupted a telephone conversation to say, “I can’t talk now. We’re having an earthquake.” Seconds later, the San Francisco clerk felt the tremor.

The earthquake had no visible effect on the oldest building at California’s oldest state university, San Jose State, but the same could not be said of the administrators working inside.

“A number of people felt it and zipped out the door,” said Joanne Rife, a university spokeswoman who also works inside the 78-year-old ivy-covered Tower Hall. “They were really sprinting.”

In addition to Monday’s incident, the San Jose area recorded a 5.1 quake on the Calaveras Fault northeast of San Jose on June 12. That earthquake followed a 5.2 temblor on the Garlock Fault near Gorman two days earlier.

Meanwhile, some Upland residents were nudged awake Sunday morning by a 4.7 earthquake, one of four lesser temblors also felt up and down California this month. The others have been in Santa Barbara, Napa and Ontario.

Because the quakes have occurred on different faults, scientists agree that the incidents are unrelated and that their timing is only coincidental.

“You have continuous activity of this nature, and it just works to relieve stresses,” said Bill Schmieder, a geophysicist at the National Earthquake Center. “If we didn’t have any activity for a long time, I might be worried, because there would be no way for the faults to work themselves out.”