South Bay shaken by 4.7 quake

‘Quite a ride in the Monterey County building. Slight shaking, then rolling motion’

HOLLISTER >> A 4.7 earthquake rattled the South Bay on Monday morning, when the San Andreas Fault’s restless tectonic plates released a small tremor of energy.

The earthquake struck at 11:31 a.m. about 15 miles south of Hollister, near the little Monterey County town of Gonzales, a rural wine cultivation region.

“Quite a ride in the Monterey County building. Slight shaking, then a rolling motion,” said Tamlyn McKenzie of Los Gatos, who was submitting a solar permit at the county building in Salinas. “Everyone felt it, but no panic. Settling down took a while.”

In the Santa Cruz Mountains, “the house shook a little,” said Larry McVoy of Los Gatos.

There were also accounts of people in Cupertino and as far away as San Francisco feeling the temblor. Authorities said there were no immediate reports of serious injuries or damage.

The earthquake is interesting to scientists because it took place in a section of the San Andreas Fault that is known to be “creeping,” said Annemarie Baltay, a seismologist with the U.S. Geological Survey in

Menlo Park.

“It typically doesn’t host large earthquakes, because it doesn’t build up the energy, then suddenly release, as when the fault is ‘locked,’ ” she said.

On the San Andreas fault, the Pacific Plate moves northwestward past the North American Plate at a rate of about two inches per year.

Constant “creep” results in many tiny rattles and a few moderate shakes. But along other parts of the San Andreas Fault, strain can build up for hundreds of years, producing great earthquakes when it finally releases and causing catastrophic damage.

The earthquake also took place in a geologically complex location, where the San Andreas and Calaveras Faults merge, she said. The epicenter was about four miles deep.

As a result of these faults, Hollister is being torn in two, because the fault runs right through the middle of town. Hollister has several cracked streets and broken curbs.

There have been three earthquakes of similar magnitude in that area since 2000: a 4.6 in 2001, a 4.4 in 2004 and a 4.6 in 2011.