For scientists, Chile becomes the ideal lab for studying seismic activity

By Juan Forero
Washington Post Staff Writer
Monday, March 8, 2010; A08

TALCA, CHILE -- When an aftershock nearly as big as Haiti's earthquake jolted this city on Friday, those already reeling from last month's huge quake shuddered in fear. But Jeff Genrich, a 53-year-old earthquake scientist from California, lolled in bed.

Staying still, Genrich said he tried to estimate the power of the seismic waves. "It didn't seem to me to be that big of a deal," he said. "I just enjoyed them."

Most people here are thoroughly rattled after an 8.8-magnitude quake, one of the most powerful on record, struck this swath of south-central Chile on Feb. 27, killing more than 450 people, buckling bridges and downing buildings. But earthquake scientists, many of them from the United States, immediately flocked to Chile to search for clues that will help them determine the coming of the next big one.

"It's very exhilarating," said Michael Bevis, a professor of geodynamics at Ohio State University who has been studying Chile's earthquake-prone geology for 17 years.

The sheer size of the quake, along with aftershocks so powerful they could be considered significant quakes in their own right, is providing scientists with a rare opportunity. Bevis, who is in the capital, Santiago, organizing teams of American scientists for field work, said the objective is to install sensors and collect data about post-quake ground movements.

"Time is very precious," Bevis explained. "If you don't get there till, say, two or three weeks afterwards, you've missed an important part of the signal, so everybody has a sense of urgency."

The first arrivals have been geophysicists and geodesists, scientists who study the curvature and movement of the Earth. Seismologists, who work with bulkier equipment, are on their way down. The quake is also going to attract structural and earthquake engineers, who will be keen to study how so many of Chile's buildings survived a quake so powerful.

"The race we're having is to get down there," Dana Caccamise, a geophysical engineer at Ohio State, said by phone from Ohio. A staff scientist at the university, he designs the kind of equipment scientists are using in Chile. "I think all branches of science will be interested in this disaster."

This quake has, to be sure, already made an impression. It changed the speed at which the Earth spins, prompting NASA scientists to estimate that the day has gotten shorter by a millionth of a second. It kicked up monster waves in the Pacific that destroyed whole towns.

Ben Brooks, a geologist at the University of Hawaii who is helping get teams of scientists to Chile, said the quake moved much of the continent. Buenos Aires moved four centimeters closer to Chile. The city of Concepcion, which was near the epicenter, moved three meters to the west.

He said about 50 data-collection stations already are strategically located along this ribbon-shaped country, which stretches nearly 2,900 miles, sandwiched by the Pacific to the west and the Andes range to the east.

Brooks said U.S. and Chilean scientists would like to install an additional 25 sensors, as fast as possible, in what he called "the rupture area," which includes a swath of pine forests and wine-growing valleys known as the Bio Bio and Maule regions.

Unlike many big quakes, this one lends itself to study. The aftershocks can be felt and measured from firm ground on the South American continent. And Chile, with its network of modern highways, is easy and safe to traverse, in spite of the damage.

"This is going to be incredibly well measured," Brooks said. "This is going to be arguably the best-measured great earthquake."

Among those who got here first was Genrich, a German-born geophysicist and staff scientist at the California Institute of Technology in Pasadena. After news arrived about the quake, he traveled to Argentina, because heavy damage had forced the closing of the Santiago airport. He then crossed overland, up and over the high Andes. His luggage had been lost en route, so the first thing he did was buy shoes and shirts.

On Saturday, outfitted in sturdy hiking shoes and shorts, he climbed into the foothills of the Andes along with a civil engineer from the University of Chile and an official from the Military Geographic Institute. They were searching for a nail-size stainless-steel pin that Chilean technicians had installed in the bedrock in 1992, precisely for measuring ground movements.

After foraging for half an hour, guided only by written directions, they found the pin and erected a tripod holding a Global Positioning System receiver. All of it is powered by a solar panel and battery. The idea is to determine how much the pin -- and the Earth around it -- moves with each aftershock.

"You would only be picking up seismic events that produce motion larger than a millimeter," Genrich said. "We want to measure the current position of this little dimple inside this nail."

Genrich said the goal is to learn exactly how this and other quakes behave.

Chile, he says, could provide important data to help scientists like him reach what he called "the Holy Grail," the ability to predict earth movements precisely. That is especially crucial here in Chile, Genrich said, because the Nazca and South American plates, which produced this latest jolt, have a propensity to build up stress and produce big quakes. Indeed, the biggest quake in history, in 1960, took place just south of here, measuring 9.5.

Genrich said that scientists have come a long way from the days when pendulums and paper rolls were used to measure ground movements. Now, they can assign probabilities of when quakes might happen and even the magnitude.

"But we have not come very far yet, to reach this goal of predicting exactly where and when and how big the next event will be," he said, noting that scientists have been energetically searching for "precursors" that definitively indicate future land movements.

"Unfortunately, the Earth has not been so kind yet, or maybe we're not looking at the right places," Genrich said.

Here in Chile, though, scientists are getting the kinds of opportunities they do not get when quakes happen under the ocean or in isolated countries where it is hard, or dangerous, to move around. They are not only using technology, such as the GPS receiver, to measure, but they are poking around bridges that shifted and studying craters that opened up.

"If you have a large event, you have a better chance of capturing more of what's happening because everything is on a larger scale," Genrich said. "You don't know exactly where it's going to happen, when it's going to happen. If it's a large event, your chances that you're in the proper area are just bigger."

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