Quake Sleuths Rush to Chile, Seeking Elusive Answers

(March 2) -- As Chile struggles to recover from Saturday's massive earthquake, engineers and seismologists from across the world are preparing to rush to the battered country to conduct invaluable scientific detective work.

The point of the effort -- generally known as a post-seismic intervention -- is to assess the existing damage and gather data relating to ongoing events, such as aftershocks. Engineers will examine how structures stood up to the 8.8-magnitude quake, while scientists hope to use GPS instruments and seismometers to gather detailed data on the aftershocks and, in some areas, the continuing, slow creep of the ground.

"We do all sorts of simulations," explains Brady Cox, a member of the group Geo-Engineering Extreme Events Reconnaissance, or GEER. "But earthquakes are so variable that earthquakes themselves are really the only opportunity to go out and see how things performed and learn new things you didn't think of."

These scientific reconnaissance teams, managed by universities and organizations such as the Earthquake Engineering Research Institute, often study affected areas in the weeks, months and years following a seismic event. The EERI has already sent two teams to Haiti. But the Chilean earthquake is unusually intriguing for two reasons. The measured 8.8 magnitude is one of the largest on record, and Chile was relatively prepared for the massive tremor.

"It's completely different from Haiti in that the building standards in Chile are actually quite good," says Cox, whose day job is as a civil engineer at the University of Arkansas. "From a structural standpoint, there is more to learn from buildings that were designed to code. You can see how they performed. Hopefully, we can take the lessons and use them to minimize damage in the future."

GEER is organizing a group to send to Chile, and Jay Berger, the Earthquake Engineering Research Institute's executive director, is also assembling a detachment of engineers, scientists and social scientists. Berger says a rapid response is critical, since what his group wants to examine goes beyond the quake's effects on large structures, such as bridges. He also hopes to gather what is known as perishable data.

For example, earthquakes can cause nonstructural damage -- loosening pipes from ceilings, say -- that will likely be fixed in the coming weeks. Cataloging these smaller but still potentially dangerous flaws in buildings could help improve earthquake codes, and potentially save lives.

On-the-ground reconnaissance allows the engineers to analyze the aftermath at a deeper level. In some cases, Cox explains, two buildings engineered to the same standards and erected in the same area might fare differently because of the ground topography or certain characteristics of the soil. This is the sort of data that can only be gathered on-site.

While engineers are mostly concerned with what has already taken place, the scientific side of these reconnaissance efforts is focused on what is still happening -- the creeping of sections of the tectonic plate that are most likely generating the ongoing seismic activity in the quake zone. The Chilean earthquake occurred along an enormous fault line where one tectonic plate is slipping beneath the other.

"During the earthquake, part of the area moves a great deal, very quickly," explains seismologist Anthony Sladen of the California Institute of Technology.

Scientists can study that main, intense event remotely, with the help of seismic and satellite data -- the tremors can be picked up by instruments across the globe. The resulting aftershocks can also be monitored from afar. As of March 1, the United States Geological Survey had registered 121 aftershocks, six of which had a magnitude of 6.0 or more.

Yet these lesser tremors aren't the only lingering effect. Over time, the areas along the fault that did not succumb to that initial, intense movement essentially play catch-up, a phenomenon known as after-slip. This slow-motion creep of these sections has to be recorded by GPS instruments and other on-the-ground tools that enable scientists to clearly measure how much, at what rate and in what direction a specific site moves.

Chilean, French and U.S. seismologists hope to set up more instruments -- they have been monitoring the zone for years and already have various measuring devices in place -- and gather more data in the coming weeks. While part of the goal is to simply learn more about large earthquakes and their effects, Sladen says there is a possibility that this information could also help scientists predict where aftershocks might concentrate following future earthquakes.

As eager as the experts are to learn from the event, they are also sensitive to more pressing concerns. "The first priority is human relief. People need doctors, medicine, water, food, shelter, before seismologists," seismologist Christophe Vigny of the École Normale Supérieure, an expert on the area, wrote in an e-mail. "But hopefully, we will all be there by the end of the week."