Word: parkfield
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Nowhere has scientific activity been more intense than near the small town of Parkfield, which sits astride a transitional zone between a segment of the San Andreas that in 1857 produced one of the largest quakes in U.S. history and another segment characterized by snail-like creep and small, quiet microquakes. Here, amid rolling hills and golden pastureland, scientists with a National Science Foundation initiative called EarthScope are building a remarkable underground observatory known as SAFOD, or the San Andreas Fault Observatory at Depth...
...effort seems bound to pay off. Last September, the Parkfield zone gave rise to a magnitude-6 earthquake whose throaty rumblings were recorded by a rich array of seismometers and other instruments, including several nestled inside a mile-deep pilot hole the SAFOD team reamed out just two years earlier. Puzzling to many scientists was the seeming absence of precursory activity, save for subtle signs that strain may have increased ever so slightly the day before...
...this point, Parkfield's seismic history seems suggestive. For more than a century, the area just south of the drill site produced magnitude-6 earthquakes on a roughly 22-year cycle--or so it seemed in the mid-1980s, when a USGS team threw a net of instruments over the area, hoping to catch the next iteration. The last quake occurred in 1966, so scientists figured the next would come around 1988. Instead, the 1966 quake was followed by a 38-year pause. Some speculate that another earthquake, which occurred on a nearby thrust fault in 1983, reset the seismic...
...approach "tail wags the dog," the tail referring to patterns of seismic activity that appear to presage large tremors. (He does not try to forecast smaller events, like the earthquake swarms that rumbled beneath Mount St. Helens before it erupted last week, or the more significant quakes that perturbed Parkfield, Calif.) At first he and his colleagues looked for strong quakes that had already occurred, then scrolled backward through years of seismic data. More recently they have been working with current seismic records as well. Their computer programs home in on small quakes that occur in temporal and spatial proximity...
Halfway between San Francisco and Los Angeles, near the tiny town of Parkfield, scientists are conducting an experiment that they hope will open the door to a new era of earthquake prediction. Along a 20-mile section of the San Andreas, researchers have sunk strain gauges up to 1,000 ft. deep into the earth and laced the surface with "creep meters" that measure rock movement. "We're listening to the heartbeat of this section of the fault very, very closely," says the Geological Survey's Thatcher. The Parkfield section of the San Andreas is unusual in that...