Scientists say quartz is key to understanding quakes( Các nhà khoa học nói thạch anh là chìa khóa cho việc tìm hiểu động đất)

(Reuters) - Underground quartz deposits worldwide may be behind earthquakes, mountain building and other continental tectonics, a discovery that may aid in predicting tremblers, according to a study released on Wednesday.

The findings by Utah State University geophysicist Anthony Lowry and a colleague at the University of London, to be published Thursday in the journal Nature, may solve a riddle of the ages about the formation and location of earthquake faults, mountains, valleys and plains.

"Certainly the question of why mountains occur where they do has been around since the dawn of time," Lowry told Reuters.

He and research partner Marta Perez-Gussinye examined temperature and gravity across the Western United States from a movable network of seismic instruments to describe the geological properties of the earth's crust.

The scientists discovered that quartz crystal deposits are found wherever mountains or fault lines occur in states like California, Idaho, Nevada and Utah.

The Utah State geoscientist said the breakthrough came after repeated testing revealed a correlation between quartz deposits and geologic events that was "completely eye-popping."

Using newly developed remote sensing technology known as Earthscope, Lowry and Perez-Gussinye found that quartz indicates a weakness in the earth's crust likely to spawn a geologic event such as an earthquake or a volcano.

"VISCOUS CYCLE"

Quartz also may account for the movements of continents known as continental drift or plate tectonics.

For example, the massive earthquake last week in Japan pushed the island nation eight feet closer to the continental United States as the Asiatic tectonic plate slid under the North American plate.

The team linked rock properties to movements of the earth, explaining how quartz contains trapped water that is released when heated under stress, allowing rocks to slide and flow in what Lowry termed a "viscous cycle."

While places like Japan, Southern California and Yellowstone National Park are known to be in the active phase of the so-called viscous cycle, other regions like the Appalachians in the Eastern United States are likely in an inactive phase.

The theory championed by Lowry could aid scientists in assessing the likelihood and strength of earthquakes in areas like Arkansas, once believed to be geologically inactive.

Another example is the New Madrid Fault near St. Louis, which unleashed an earthquake strong enough to reverse the flow of the Mississippi River in 1812 but has since gone dormant.

The research also may provide clues to everything from safe siting of nuclear power plants to the structural demands of large dams.
"We're groping around the elephant at the moment," Lowry said. "We're basically seeing a different piece of information and this piece is going to be really key to understanding what's going on."

Lowry already has launched a second, large-scale study in the Midwest, including the New Madrid Fault, to test the team's theories and is eyeing a separate project in the Appalachian Mountains.

(Editing by Dan Whitcomb and Jerry Norton)
http://www.reuters.com/article/2011/03/16/us-earthquakes-quartz-idUSTRE72F87D20110316?pageNumber=2