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After the Quake

Rapid Deployment Will Capture Vital Aftershock Data In Chile

SOCORRO, N.M. March 26, 2010 – New Mexico Tech is at the forefront of earthquake studies in the aftermath of the devastating earthquakes in Chile.

Tech scientists from the IRIS PASSCAL Instrument Center, working with scientists around the United States and in Chile, this week begin deploying an array of 60 seismic stations to the earthquake-ravaged region in central Chile.

George Slad, an engineer with the IRIS PASSCAL Instrument Center at Tech, and his colleague Dr. Anne Meltzer prepare a broadband seismic sensing station for installation at a farm house near Cumpeo, Chile.

 

George Slad of New Mexico Tech (left) piqued the curiosity of a local farmer when he asked permission to locate a seismic station on their property. In ideal circumstances, sensing equipment would be placed far from 'cultural noise,' but in rapid deployment, security and quickness take precedence. This was the sixth station Slad's team deployed in less than a week.

Thanks to special rapid-deployment funding from the National Science Foundation – and quick work by PASSCAL Instrument Center engineers at Tech – three New Mexico Tech engineers have joined colleagues from Germany, France and Chile for several weeks of fieldwork in the aftershock zone. The Incorporated Research Institutions for Seismology, which supports the Instrument Center, successfully applied for NSF funding to deploy the array with leadership from researchers from several U.S. universities.

Chile was rocked by the fifth-largest earthquake ever to be recorded on February 27. The quake registered 8.8 on the Moment magnitude scale, and is currently generating thousands of sizable daily aftershocks, many of which have been greater than 5.0 on the Richter scale.

New Mexico Tech engineers Bob Greschke, George Slad and Brian Bonnett will spend about a month in Chile setting up the sensor network.

Dr. Rick Aster, the principal investigator for the PASSCAL Instrument Center, said the main goal is to improve imaging capabilities in the region of the aftershock seismic activity in Chile and to record their geographically varying ground motions.

“We want to get a better handle of the aftershock distribution and its stress-related and other geophysical effects,” said Aster, who is a professor of geophysics and the chair of the Earth and Environmental Science Department at Tech. “This is really an historic event, because earthquakes of this size only occur a few times a century. We’ll record seismic signals that will help us study the structure of the Earth’s mantle and crust in the Andes. We hope to see ongoing changes in the properties of the Earth as the system readjusts to this huge earthquake. This earthquake is also highly relevant to learning about the physics and damaging effects of giant earthquakes that will occur in the U.S. in the future”.

Engineers George Slad and Brian Bonnett said this project is different than most because of the accelerated nature. They usually have several months to plan an expedition and prepare the instruments for deployment. Bonnett, who specializes in polar engineering, said the short preparation time is abnormal.

“We’ve had only two to three weeks to get prepared,” Bonnett said. “We’ve had people working on the instruments every day, pretty much non-stop. When we go to Antarctica, every nut and bolt is ready. For this project, we’ll have to find a lot of equipment and tools in Chile.”

Slad said instrument specialists at the PASSCAL Instrument Center worked intensely for three weeks to prepare the seismometers for deployment, pack the instruments and arrange shipping.

The expedition scientists also expect to encounter obstacles created by the earthquake. Prior to departing from Socorro, Bonnett said colleagues already in Chile had reported that transportation is a heavy slog. A seven-hour drive is now taking a full day due to heavy traffic on the remaining good roads.

Slad said he expects that the team members will have to improvise more than usual. For most deployments, the chief investigator arranges to transport batteries and enclosures from Socorro. Project organizers were not able to acquire and arrange transport for these items, so the expedition team will purchase equipment in Chile.

“Supplies may be short in Santiago,” Slad said before leaving Socorro. “We’re going to have to think on the fly.”

The six-person team includes the three Tech specialists and three university scientists from the United States. The group will split up into three two-person teams, each of which will have a Chilean driver and scientist. Slad said the team will divide the target area into three zones and each team will deploy about 20 seismic stations. A typical work day will start early and end late. The scientists have identified ideal locations to place the stations, but the expedition team members will be responsible for selecting exact locations.

“The scientist selects each location in a general sense,” Slad said before leaving Socorro. “But we’ll look for sites that are protected and on private land. Occasionally things get stolen, so we want to avoid that. Or we could have cattle chew on cables, so we want to make sure they are well-protected from animals.”

Via e-mail from Chile, Slad wrote that his team was having good fortune finding willing landowners. His team had installed six stations during the first week of deployment. He wrote that residents at times would stop what they were doing -- like fixing earthquake damage to their own homes -- to help install the seismic equipment.

As the aftershocks continue in the Andean region, scientists affiliated with IRIS will use the seismic sensor array to develop seismic tomographic maps of the Earth’s interior. The IRIS PASSCAL Instrument Center is the largest lending library of seismic instruments in the world. The Center has more than $20 million of top-of-the-line “broadband” seismic sensors and another $50 million of other seismic equipment, all funded by the National Science Foundation and U.S. Department of Energy.  

“We are the international standard for portable seismic research instruments,” said Aster. “Other nations are trying to catch up, but we manage, by far, the world’s largest pool of this type of state-of-the-art research instrument.”

The current expedition to Chile is one of over 70 IRIS-supported experiments ongoing worldwide. "By examining the changes within the Earth in and around the fault zone in Chile, scientists expect to improve the general knowledge of the mechanisms that drive seismic activity," Aster said. Lessons learned in Chile can be applied to other seismically active regions, specifically the Pacific Northwest.

“The Andean region is in many ways analogous to the Pacific Northwest,” Aster said. “The megathrust earthquake expected in the Cascade region of Oregon and Washington may have a lot in common with this earthquake. It behooves us in the United States to study this thoroughly.”

– NMT –

By Thomas Guengerich/New Mexico Tech