Strong quake hits Central California

PARKFIELD, Calif. - A strong earthquake with a preliminary magnitude of 6.0 struck Tuesday along the San Andreas fault in a place known as California's earthquake capital. Some structures were damaged in the immediate area, but no injuries were immediately reported.

The earthquake, which struck at 10:15 a.m. PDT, was centered 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.

More than 160 aftershocks followed in quick succession, one with a preliminary 5.0 magnitude and four others at 4.1 or above. 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.

"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 in Parkfield. "Trees shaking like brooms, and dust coming from everywhere."

Five or six of Miller's buildings - including his home - were damaged by the quake, which also tipped over about 300 cases of wine. Most of his water pipes burst, and so much was thrown out of place in the ranch's mechanic shop that he couldn't even walk in to assess the damage, he said.

"I looked at the 10,000-gallon water tank, and there was water shooting 30 feet away," said Miller, who ran to the lawn with his wife when the first wave hit.

More than four hours after the main earthquake, the state Office of Emergency Services hadn't received any reports of injury or major damage. "The aftershocks are tracking toward the northwest, which is good, according to the scientists, because it appears it is not a precursor to something larger," said Eric Lamoureaux, an OES spokesman.

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.

Laurie Batson, of Parkfield, was out horseback riding with her husband on their ranch when the quake struck.

When they returned to her house to check for damage, they saw a couple of cords of wood that had just been stacked had been knocked over and a horse trailer was knocked off its block. But nothing could have prepared them for what they saw when they went inside.

Two large brick fireplaces in their 30-year-old home had completely collapsed into their living room, leaving large chunks of concrete and brick strewn across the floor. Glasses from their kitchen cabinets flew out and crashed to the floor. The microwave tumbled over. The television set was face down, cracked, on the ground.

The china hutch had swung open and dishes had fallen into the hallway. Large cracks had opened in the ceiling. And in the kitchen, some debris fell on to their stove turning it on high.

"It's a good thing we came home or else the house would have burned down," Batson said.

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.

Parkfield, population 37, is one of the world's most seismically active areas, sitting at the boundary of a creeping section and locked section of the San Andreas fault - the meeting of the Pacific and North American plates as they grind along 800 miles through California.

The town was shaken by six earthquakes of at least 6.0 between 1857 and 1966 - one approximately every 22 years. Because of the regularity with which countless smaller tremors constantly rattle the area, the USGS about two decades ago installed seismometers, strainmeters, creepmeters and just about every other tool used to study temblors there. The equipment is monitored remotely as part of a long-term quake research project named the Parkfield Experiment.

Based on the spacing of the previous Parkfield 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," said Michael Blanpied, associate coordinator with USGS's earthquake hazards program in Reston, Va. "This will probably be the most well-recorded earthquake in history."

The USGS estimate was strengthened several times Tuesday, from 5.8, or "moderate," to 6.0, the threshold for a "strong" earthquake. Preliminary magnitudes are determined by seismographs across the planet, and often change as scientists pinpoint where the epicenter is and interpret the data.

A magnitude 5 quake can cause considerable damage and a magnitude 6 quake severe damage, though problems are generally far less severe in remote areas and places with strong building codes.

"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, many residents of the area have taken precautions to protect their property and valuables from the next inevitable quake.

"I respect them, let's put it that way," Mary Vanderwert, 57, said by telephone from her Paso Robles home, where she experienced Tuesday's earthquake as a series of ripples and vibrations. "It just tickled your feet and then all of a sudden it's jerking and then the whips started. ... Here comes another one, hang on."

Christy Gieseke, 49, a rancher in nearby San Miguel, said the earthquake spooked her horses - and her as well.

"I had just got out of the shower and ran outside in my dishtowel. My chandelier was shaking. You could hear the ground," Gieseke said. "It was totally scary. I came in and I decided I better get my clothes on real quick."

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. Drivers into town pass a sign reading "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, a lifelong resident and owner of the Parkfield Cafe, where food spilled out of the cupboards Tuesday. "I'll take my earthquakes over those hurricanes any day."

On the Net

http://earthquake.usgs.gov/