Inside an Earthquake: Geologists Penetrate Fault Zone 2 Miles Down
By Robert Roy Britt
LiveScience Senior Writer
posted: 04 August 2005
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Scientists breached a major underground earthquake zone this week in Southern California by drilling a hole more than 2 miles down into the San Andreas Fault.
The hole will be lined with steel and concrete, then instruments will be installed to monitor the many small and large temblors that occur on the fault.
Geologists at the drill site near Parkfield, Calif., the self-proclaimed earthquake capital of the world, reported Tuesday that the drill rig had reached the depth where local earthquakes originate. "Our first indication of entering the fault zone was a modest increase in drilling rate starting at about 2:30," according to the project's online daily log. The shift marked entry into a less rigid area of rock.
Sensors also picked up increases in radon, hydrogen, carbon dioxide, all signs that the fault zone had been penetrated.
The drill was at 12,452 feet, or 2.3 miles (3.8 kilometers) down.
"We now have the first opportunity to measure directly the conditions under which earthquakes begin and grow," said Herman Zimmerman, director of the National Science Foundation's (NSF) earth sciences division.
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http://www.livescience.com/forcesofnature/050804_san_andreas.html