published Saturday, November 19th, 2011

Scientists will place earthquake monitors and study Georgia geology

ATLANTA — Researchers in a nationwide study of earthquakes soon will place instruments beneath the Georgia red clay and in other eastern states as they seek to learn what causes them and where they might strike.

Scientists say an August earthquake in Virginia, which cracked the Washington Monument, has led to a renewed emphasis on trying to understand more about what lies below the Earth’s surface in eastern states.

On Nov. 9, a 2.7 magnitude earthquake hit Dalton, Ga. Experts said the quake, reported by Whitfield and Catoosa county residents at 11:45 a.m., was centered a mile west-southwest of the city and about three miles underground. It was felt from Dayton, Tenn., to Atlanta and from Gainesville, Ga., into Alabama.

“It will help us to understand where the earthquakes are, where the faults are and generally get a clearer picture,” said Bob Woodward, director of USArray, a national project between multiple universities and government agencies to monitor and map the earth’s movements. “You bring the whole structure of the continent into much clearer focus.”

In Georgia, instruments will soon blanket the state, allowing researchers to see for the first time how seismic activity is connected to other regions.

“We will get some unprecedented high-resolution images,” said Lara Wagner, assistant professor of seismology and tectonics at the University of North Carolina at Chapel Hill. “It’s real science in the sense that we’re seeing things that nobody has seen before.”

Wagner is part of a team of scientists working on a project in Georgia that’s related to the broader efforts of USArray, and uses some of the project’s equipment.

Wagner and her colleagues are now installing dozens of seismometers across the state, in addition to the hundreds being used as part of the nationwide USArray project.

About half of the Georgia instruments are already in place, and the other half will be installed in May, Wagner said. They’re expected to continuously monitor the Earth’s movements until May 2014.

A focus of the Georgia research is the area where scientists believe an ancient supercontinent broke apart.

“We don’t really understand how continents form and how they break apart, and in particular where they decide to break apart when they do and how stable those old structures are,” she said.

In Georgia and other states, knowledge of earthquakes is far more limited than in the western U.S. In California, for instance, the reasons for Earth’s upheavals are far more obvious because of a well-known plate boundary, Woodward said.

“We have a very poor understanding of what causes East Coast earthquakes,” Wagner said.

“We can’t even begin to understand what’s causing earthquakes on the East Coast until we know what’s down there,” she added. “The very basic science is lacking — we just don’t know how the crust of the East Coast is put together.”

Other researchers working in Georgia include Brown University seismologist Karen Fischer and Rob Hawman, an associate professor in the University of Georgia’s geology department. Their project is known as S.E.S.A.M.E., an acronym for the Southeastern Suture of the Appalachian Margin Experiment.

Woodward says he’s excited about the potential for discoveries in Georgia and states in the Appalachian mountains.

He’s also hoping the broader USArray project will improve understanding of a region in southeast Missouri, where a series of ferocious earthquakes struck in 1811 and 1812 in an area known as the New Madrid fault.

There’s been debate among scientists over the potential for another devastating strike there, which could threaten modern skyscrapers, historic buildings and millions of people in cities such as Memphis and St. Louis.

“The question now is, is that area reloading for another one?,” Woodward said.

“Scientifically it’s quite an interesting debate,” he said. “I’m certainly hopeful that all the instruments may shed some light on it.”

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