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NewsvineStanford geologists were part of an unveiling yesterday of the first rock samples extracted earlier this month from an underground shaft beneath the San Andreas Fault, effectively setting a milestone in geology with possibly great scientific consequences.
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The four-inch wide cylindrical samples of ash-colored rock were lifted from a borehole that intersected the San Andreas Fault at an angle roughly 2.5 kilometers beneath the tiny town of Parkfield, located at the center of the California Central Valley. Parkfield, known as the “Earthquake Center of the World,” is particularly seismologically active, and researchers said the removed rock would offer an unprecedented cross-section look at how tectonic plates rub together as earthquakes are born.
“This physically takes us down into the earth where that instantaneous earthquake deformation occurs,” National Science Foundation (NSF) Researcher Kaye Shedlock said while describing the drilling process at a press conference yesterday morning. Before a crowd of two dozen journalists and Bay Area television cameramen, Shedlock explained that for decades, geologists have wondered about the dynamic workings, mineralogical makeup and presence of fluids along the Earth’s faults.
“These questions could only be answered by going down to where the action is,” Shedlock said.
Stanford geophysicist and principal investigator Mark Zoback exuberantly compared geologists’ extraction of the rocks to astronomers obtaining “moon rocks” for the first time. Scores of geologists from across the world are expected to descend upon Stanford in December for an official unveiling to scientific circles, and the University will likely share some material with dozens of research groups, the researchers said.
While researchers acknowledge that the elusive science of earthquake prediction remains a distant dream, they may now be able to at least identify some usable predictors.
The borehole extended through an area that annually sees hundreds of thousands of tiny earthquakes, some with all the force of a textbook falling to the ground. The scientists say that because even the biggest earthquakes — such as the 9.3 magnitude quake off the Indonesian shore that triggered the devastating tsunami in late 2004 — begin as tiny slippages along the faults, the extracted rocks will effectively be snapshots of nascent earthquakes.
Stanford, in conjunction with the U.S. Geological Survey (USGS) and the NSF, began to drill in 2004 as part of the first phase of the $25 million San Andreas Fault Observatory at Depth (SAFOD) project. The San Andreas Fault is of particular interest to researchers because it is very “slippery” — meaning plates slide against each other unusually frequently. But for some reason, this friction often does not cause the massive earthquakes that would occur elsewhere.
The samples extracted by SAFOD may have already provided an effortlessly vivid answer to this old question of how the plates gently slide. The samples on exhibit yesterday revealed streaks of a bluish-green mineral in the rock called serpentine, which is made of remnants of ancient oceanic crust. Serpentine, incidentally, forms the slippery mineral talc — the smooth stuff of baby powder — when subjected to high temperatures and water with silica.
And just like that, geologists have made at least some headway on a few of the most compelling questions that previously stalled the field for decades.
“We have the ability to answer long-standing questions that people have puzzled about for 40, 50 years,” Zoback said. “The future is indeed bright. The science will make tremendous advances by having this material.”