Everyone in southern California is worried aboutearthquakes, and wonders when "The Big One" will hit.Geologists are trying to learn more about earthquakeprediction in Parkfield, California, the "earthquake capitalof the world." Stanford geologist Mark Zoback and his teamat the United States Geological Survey (USGS) have begundrilling a hole a mile deep into the San Andreas Fault,which runs underneath Los Angeles. They?re digging slowlyand carefully, and listening for rumbles along the way.
If they manage to complete the hole, they?ll have the firstunderground earthquake observatory in an active fault zone.It?s part of a project called the San Andreas FaultObservatory at Depth (Safod), which is designed to collectdata about the fundamental processes that cause earthquakes.
Right now, all seismic instruments sit on the Earth'ssurface or in shallow boreholes. By placing instruments inthe heart of a fault zone, Zoback hopes to monitorearthquake activity where it happens. "It's like using astethoscope and listening very, very carefully,? he says.
The scientists want to find out what forces act on a faultbefore, during and after earthquakes. This includes chemicalchanges that might precipitate an earthquake, as well asphysical stress. They?re gathering this date in order todetermine if earthquakes can be prevented. Right now, thescience of quake prediction is very inexact. "There is noway reliably to provide short-term warning of earthquakes,"says Sayfod investigator and USGS geologist Stephen Hickman."There have been many more failures than successes."Currently, geologists can only provide 30-year "hazardestimations" of an earthquake occurring on a particularfault in a particular area, he says.
The hard granite of the San Andreas means the drilling goesslowly. Once they?ve dug about a mile deep, they hope tostart a second hole that will be four times deeper, but theyneed money from Congress in order to do it.
Inside these holes, a range of seismometers will record theforce of earthquake shake, while meters and sensors measureground deformation and fluid pressure. Some scientists thinkchanges in fluid pressure may trigger an earthquake.
Parkfield is built on top of a particularly active sectionof the San Andreas Fault where the plates continuously"creep. " As a result, the town experiences small tomoderate-sized quakes regularly, which makes it a "naturallaboratory," says Hickman. Parkfield is 10 years overdue forits regular magnitude six quake. These have occurred every22 years since 1857. Scientists hope it doesn?t happen untilthey get their hole finished.
Right now, predicting earthquakes is like looking into acrystal ball. You can learn all about that from Ambrose Hawkin ?Exploring Scrying?,click here.
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