Minor Damage Reported in Gilroy Quake

A plate-glass window shattered, a few other windows broke and some goods were thrown off shelves, but no injuries were reported in Friday night’s magnitude 5.1 earthquake near Gilroy, south of San Jose, in what has been one of the most seismically active parts of the state.

The temblor, at 10:29 p.m. Friday, was centered seven miles east-northeast of Gilroy, two miles from the epicenter of a magnitude 5.9 temblor that injured 16 people in Gilroy and Hollister on Aug. 6, 1979.

The quake was felt as far as Santa Rosa, more than 100 miles to the north, and in the San Joaquin Valley, 75 miles to the east. It rattled windows and dishes in San Francisco, but caused no damage.

The U.S. Geological Survey’s David Oppenheimer said Saturday that there were very few aftershocks from the temblor. That portion of the Calaveras Fault may have been relieved of stress, and there may be no more such moderately strong quakes in the Gilroy segment in the near future, he said.

It was the eighth quake of similar or stronger magnitude since 1974 on the Calaveras Fault, which extends along the foothills of the Diablo Range from Danville east of Oakland, south past San Jose to Hollister.

Quake scientists from the Geological Survey noted Saturday it is the area north of Gilroy that historically has generated the strongest quakes along the fault line.

Three Geological Survey scientists--Oppenheimer, Allan Lindh and William Bakun--in a 1990 paper in the Journal of Geophysical Research, said the next temblor in the magnitude 5 range on the Calaveras Fault would occur near Gilroy. Their projection was borne out Friday night.

A stronger Calaveras Fault earthquake, magnitude 6.2, injured 24 people and caused $5 million to $10 million damage, mostly in Morgan Hill, 10 miles north of Gilroy, on April 24, 1984. A 6.6 temblor was centered in the same area July 1, 1911.

The 7.1 Loma Prieta earthquake on Oct. 17, 1989, not far away in the Santa Cruz Mountains, was close to the San Andreas Fault on a different system of seismic stress.