Saturday, September 8, 2007

Tech researchers use explosives to study volcanoes

Argen Duncan El Defensor Chieftain Reporter, aduncan@dchieftain.com

Explosives and a volcano may sound like a dangerous combination, but New Mexico Tech researchers with seismometers are aiming to use them to gather information about volcanoes that could help people.

The scientists hope to use seismology to begin developing an image of the inside of the Antarctic volcano Mount Erebus and fine-tune techniques to do so during a few months at the bottom of the world. The information would help show how the volcano works, said Professor of Geophysics Richard Aster.

Kyle Jones, senior who plans to visit Antarctica for the third time, said the knowledge they gain from Mount Erebus could apply to other volcanoes.

"They don't all work the same, but the processes are similar," he said.

Aster said volcanoes are hazardous and scientists should understand how they work, especially if the ones near people.

Doctoral student Hunter Yarbrough is leading the research for her dissertation. She plans to put out a total 25 temporary seismic stations in rough rings at two different elevations on the upper half of Mount Erebus. Five permanent seismic stations are already there.

"It's the largest deployment of broadband seismometers that has been done on Mount Erebus," Yarbrough said.

The researchers plan to use the instruments for both active and passive seismology.

In passive seismology, they sit and listen to eruptions, earthquakes, iceberg movements and ice quakes, Yarbrough said. In active seismology, the instruments monitor seismic waves from explosions the researchers set off.

"And that can tell us something about what's inside the volcano," Yarbrough said.

Jones said they would drill a hole, pull out the ice core and stuff the hole with explosive fertilizer like the material used in the Oklahoma City Bombing. She said the fertilizer is environmentally safe as an explosive, and researchers would drill holes on several sides of the mountain.

The procedure is like a CAT scan, Jones said.

Aster said researchers would measure when the seismic waves arrived at the instruments after the explosion, which lets them infer where areas of heat and magma are. Assistant Professor of Geophysics Cathy Snelson, who plans to handle the explosions, said the velocity of the waves also relates to types of rocks and liquids.

Snelson said the researchers don't know how big of a blast they will need to get the proper data. They plan to do a series of tests.

Also, Jones said people could only access the area for the lower planned ring of seismometers, which are 6,500 feet in elevation, by helicopter. They must fly in parts as quickly as possible before bad weather comes.

Besides the temporary seismic stations, Yarbrough said the group intends to lay out a "streamer," a string of geophones, during explosions.

This particular streamer is to be almost a mile long and contain 60 geophones.

Aster said it would ideally pick up energy arriving at different points on the line and provide more data about the volcano.

"This is sort of a proof of concept test of this equipment," he said.

If the blasting technique works well, the researchers plan to return next year with more instruments to get a clear picture of the inside of the upper part of Mount Erebus.

Aster wants to use all information possible to get an image. Other techniques, such as recording background noise and waves from earthquakes around the world, need a longer recording time.

Yarbrough said all members of the team would do manual labor related to the experiment.

"Otherwise we don't operate," she said.

Team members are scheduled to visit Antarctica at various times for stays of different lengths from October through January.

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