updated 9/30/2004 10:45:04 AM ET 2004-09-30T14:45:04

Earthquakes on two separate faults rattled Central California a day after a 6.0-quake jolted the region. No major damage or injuries were reported.

The temblors Wednesday were close enough in time and location to leave scientists wondering about a possible link. A magnitude-5.0 earthquake shook Kern County, hours after a pair of aftershocks from Tuesday’s quake rattled the earth more than 100 miles away in Monterey County.

The Kern County temblor triggered a rock slide on a state highway, but there were no reports of damage or injury, and the road was quickly cleared.

That earthquake struck 17 miles northeast of Arvin shortly before 4 p.m., said Anthony Guarino, a seismic analyst for the California Institute of Technology in Pasadena.

Quake not an aftershock
The quake was felt from Sacramento to Las Vegas. It was not an aftershock from Tuesday’s quake in Parkfield, 150 miles northwest, seismologists said.

There have been about 600 aftershocks to the Parkfield quake, including six of at least 4.0. Two of the biggest, 5.0 and 4.5, shook the region Wednesday morning, about 5 miles northwest of Parkfield, and the largest rattled window blinds in San Jose.

Susan Hough, a U.S. Geological Survey seismologist, said the aftershocks would likely dissipate, instead of signaling a larger quake to come. The deadly 6.7-magnitude temblor that hit the Northridge area of Los Angeles in 1994 was preceded by an earthquake sequence in the Salton Sea area.

Arvin, a rural community of about 14,000, is 79 miles north of Los Angeles and lies at the eastern end of the White Wolf fault, which ruptured in a magnitude-7.5 quake in 1952.

Tiny Parkfield, population 37, is on an area of the San Andreas fault that is a seismic hot spot, among the most-monitored quake sites in the world.

Tuesday's quake could be a boon to researchers who hope intense scrutiny of the state’s earthquake capital may help predict future temblors.

The magnitude 6.0 earthquake struck at 10:15 a.m. Tuesday, about halfway between San Francisco and Los Angeles, seven miles southeast of Parkfield and 21 miles northeast of Paso Robles, according to the U.S. Geological Survey. A major quake in the same area killed two people last year.

A seismic hot spot
The area of the San Andreas fault where the quake struck is a seismic hot spot that has produced similar temblors every two or three decades and is among the most-monitored quake sites in the world.

“It’s going to be a lot of data that we can look at,” said Andy Snyder of the U.S. Geological Survey. “It ensures a good payoff for all the work that’s been done by the USGS, all the university groups and foreign research institutes that have set up experiments here.”

Dozens of sensors — seismometers, strainmeters, creepmeters — dot the remote, sparsely populated region. Drilling is underway there to go 1.4 miles down into the bowels of the 800-mile-long fault that forms the boundary between immense geological plates that grind and produce ground movement.

“This will probably be the most well-recorded earthquake in history,” said Mike Blanpied, associate coordinator with the U.S. Geological Survey’s earthquake hazards program in Reston, Va. “The jury is still out about whether the earth gives out reliable signals about whether an earthquake can be predicted.”

The initial, 10-second quake was felt along a 350-mile stretch, as far north as Sacramento and as far south as Santa Ana, southeast of Los Angeles.

‘Trees shaking like brooms’
“Things were shaking so bad you couldn’t tell where to go next,” said Parkfield Vineyard owner Harry Miller, who grows 170 acres of wine grapes. “Trees shaking like brooms, and dust coming from everywhere.”

Ready to rumble?Five or six of Miller’s buildings — including his home — were damaged by the quake, which also tipped over about 300 cases of wine.

“I looked at the 10,000-gallon water tank, and there was water shooting 30 feet away,” Miller said.

Based on the spacing of the previous earthquakes, geophysicists had expected another earthquake of magnitude 6.0 or greater to hit Parkfield 15 years ago. But it didn’t happen until Tuesday.

“It was very much the anticipated earthquake — the anticipated magnitude and the anticipated section of the San Andreas fault,” Blanpied said.

Scientists put the chance of another similar or larger quake striking in the same area this week at 5 percent to 10 percent, said USGS geophysicist Andrew Michael.

Tuesday’s quake, which occurred at a depth of 4.9 miles, was a “strike-slip quake,” which means it caused the ground to move horizontally, said Kate Hutton, a seismologist at the California Institute of Technology in Pasadena.

The USGS estimate was strengthened several times, from 5.8, or “moderate,” to 6.0, the threshold for a “strong” earthquake. A magnitude 5 quake can cause considerable damage and a magnitude 6 quake severe damage, but damage is usually far less in areas with strong building codes.

‘This is earthquake country’
“This is earthquake country. It’s a larger earthquake than what usually occurs, but it’s not unprecedented,” USGS spokeswoman Stephanie Hanna said. “We expect big earthquakes in this area, but don’t know when they’ll occur.”

Last December, a magnitude-6.5 earthquake jolted the Central California coast, pitching an 1892 clock tower building onto the street and crushing a row of parked cars. Two people were killed in the state’s first fatal quake since the 6.7-magnitude temblor that hit the Northridge area of Los Angeles in 1994.

Since then, area residents have taken precautions to protect their property and valuables from the next inevitable quake.

The very few residents of Parkfield — a half-dozen buildings on either side of a street in a valley surrounded by oak-studded hills — pride themselves on the area’s seismic activity. A road sign reads: “Now entering the North American plate.”

“The thing about the San Andreas fault is, you have to appreciate it because it’s what made California the most spectacular state there is,” said John Varian, owner of the Parkfield Cafe, where food spilled out of the cupboards Tuesday. “I’ll take my earthquakes over those hurricanes any day.”

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