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Parkfield, Often Shaken, Is Really Stirred by 6.0 Quake

Earth scientists and aftershocks swarm the seismically active town after Tuesday's temblor.

September 30, 2004|Richard Fausset and Usha Lee McFarling | Times Staff Writers

PARKFIELD, Calif. — Over the better part of two decades, the ranchers of this lonely patch of rolling grassland and the curious professors stationed here have learned to accommodate each other.

The scientists remember to shut cattle gates behind them and the ranchers abide all manner of machinery poked into their pastures in hopes of capturing a major earthquake on the San Andreas fault -- long predicted but long delayed in arriving.

With strong aftershocks from Tuesday's 6.0 magnitude quake still shaking the Monterey County town roughly 20 miles northeast of Paso Robles, both groups mingled with bemusement and triumph Wednesday at the Parkfield Cafe, where the motto is: "Be Here When It Happens."

"For me, this is like Christmas," said geophysical technician Chris Dietel, who jumped into his truck to check his far-flung U.S. Geological Survey data recorders. "I've been coming down here for the last 17 years, waiting for all the seismic data I can get."

Curiosity seekers rolled up periodically to the cafe, the only eatery in a town that consists of little more than a firehouse, a mobile-home library and a log-sided inn.

Heike and John Van De Wouw drove 45 minutes from Templeton. "Every time we have tourists from out of town, we bring them here," said John, 72. "We're hoping that an earthquake will happen, but it never has."

On the contrary, it's the stunning regularity of small earthquakes that draws scientists to a town settled by sheep and cattle ranchers in the mid-19th century.

The San Andreas runs for 800 miles from northern Mexico to the top of California, and Parkfield sits in a unique stretch of it. To the north of the town, the fault tends to creep along without producing big quakes. To the south, it tends to stay locked until it slips to produce huge earthquakes, including the state's largest: the Fort Tejon quake of 1857, estimated at an 8.0 magnitude.

Parkfield's location in a transition zone of the fault has long been considered the best place to "trap" an earthquake. In 1978, two U.S. Geological Survey seismologists predicted a 6.0 quake would occur on the stretch by 1993.

Scientists started wiring the fault with sensors and gauges, hoping to catch a quake in the act. Then they waited -- and waited and waited, sometimes fending off critics who questioned the wisdom of keeping so much monitoring equipment in one place with nothing to show for it.

Until Tuesday.

"Finally," said John Langbein, the chief scientist for the Parkfield project, from his office in Menlo Park, Calif. "It's a relief."

Langbein scrambled to join the commotion in Parkfield on Wednesday. "First, I've got some instrument chores. Then I'm going to look at some data," he said.

Ahead of him, Doug Myren, a U.S. Geological Survey geologist, steered his cluttered SUV down a ravine on private ranchland. He stopped by a corral of boxes and transmitters and recovered a magnetic tape that recorded Wednesday morning's 5.0 and 4.5 aftershocks, transmitted from a "creep sensor" buried 1,000 feet below.

"Oh, I'm jazzed that after all this work, something has finally come to pass," he said.

The area around Parkfield is littered with about 100 such instruments that measure creep and strain and how the earth buckles and bulges. Other instruments look at how earthquakes affect water levels in nearby wells. Still others monitor slight fluctuations in magnetic fields caused by stress and deformation of rocks.

The passage of time, however, has taken its toll on instruments that date to the mid-1980s: Two strain meters "died of old age," Langbein said. "The crying shame is one of them would have been directly adjacent to" the center of the earthquake.

Still, there is plenty of data to go around. "It's going to be the best-recorded earthquake in history," said Kate Hutton, a staff seismologist at Caltech.

The newest project is the San Andreas Fault Observatory at Depth, a $20.5-million effort to drill 2.4 miles into the fault and provide around-the-clock monitoring of an active quake zone.

Though Tuesday's quake came 11 years late, according to predictions, it came too early for the drill crew, which plans to start recording data next summer. Scientists had hoped to be able to get recordings from the heart of the fault zone during a 6.0 quake, said Steve Hickman, a USGS researcher who is co-director of the project. But the project will still glean other information about the fault, he said.

Townspeople, used to taking earthquakes in stride, were pleased that the scientists had finally gotten what they'd long been coming for.

Mary Winfree, 59, said a lot of cowboys in the area are well versed in the finer points of plate tectonics.

"Everyone's a geologist out here. We can't help it," she said. "If you live on a conveyor belt, you want to know where it's going and how fast."

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