Geotimes - August 2002 - Seismic Testimony

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Forensic Seismology
Seismic testimony in pipeline explosion

Seismologist Keith Koper is throwing around phrases like “punitive damages” and “legal liability” as naturally as he would “seismic propagation” and “Rayleigh waves.” Koper, an assistant professor at St. Louis University, is beefing up on his legal know-how and lending his seismic expertise to a lawsuit surrounding a natural gas pipeline explosion that killed 11 people in New Mexico.

On Aug. 19, 2000, a natural gas pipeline exploded in southeastern New Mexico near the Pecos River. Eleven nearby campers died. Just how, when and why the explosion happened have all been in question since the tragic accident two years ago.

The Aug. 19, 2000, natural gas pipeline explosion in southeastern New Mexico created a crater 86 feet long, 46 feet wide and 20 feet deep. An analysis of the explosion’s seismic signals is providing details on how the accident occurred. Image courtesy of Keith Koper.

“It turns out that this disaster was recorded by two seismic arrays that were located nearby, and the seismic data recorded the accident in pretty nice detail,” Koper explains. The seismic data show three distinct sources for the event: the initial blowout and two subsequent ignitions. It also shows when the gas company turned off the flow of gas and how long the campers had to react between the initial blowout and the primary ignition. That time span, about 25 seconds, is crucial to determining the gas company’s liability. And so the lawyers for the victims’ families called upon Koper to testify at a deposition in June for a lawsuit between the families and the natural gas company, El Paso Natural Gas. The National Transportation Safety Board has already fined El Paso $2.5 million for negligence.

The New Mexico pipeline explosion investigation is one of several of Koper’s forensic seismology research projects — analyses of seismic recordings from unanticipated, man-made sources, so-called exotic sources. He teamed with Terry Wallace of the University of Arizona and others to put together seismic data to unravel the events surrounding the sinking of the Russian submarine Kursk in 2000 (Geotimes, February 2001). They have also analyzed the seismic signals from the 1998 bombing of the U.S. Embassy in Nairobi, Kenya, that killed more than 200 people. Koper and Wallace were able to constrain the amount of explosives used. As the number of seismometers recording real-time data increases globally, and with the wide availability of the data on the Internet, this type of work is becoming more possible.

“We can be the technological equivalent of a global neighborhood watch,” said Greg van der Vink of the Incorporated Research Institutions for Seismology, during a forensic seismology session at the American Geophysical Union spring meeting in Washington. And that global monitoring has new relevance with the U.S. war against terrorism. Geophysicists always have their “ears to the ground” and can help to provide data that might not otherwise be available, said Wallace, also at the meeting.

Much of the seismic data on exotic sources simply corroborate information from standard investigations. “There’s a lot of people in the community that probably feel like it might be fun or interesting to model these sources, but that you cannot really get any tangible, distinct information. And I feel like at least with the Kursk and the pipeline explosion, there is actually unique, distinct information available from seismic data,” Koper says.

For the Kursk sinking, the seismic data provided the only public account of what really happened. “In the case of the pipeline, the data is even a little bit more definitive in the timing and nature of these events in that there’s no other way at all to figure out this time delay between the blowout and the ignition,” he explains. Witness reports and crater investigations could not provide the necessary information.

“The 25 seconds comes into play in one respect because the amount of punitive damages in New Mexico that a company can be held liable for due to negligence is related to the amount of time that people were in mortal fear for their life,” Koper says. The families of the victims can sue for the pain, suffering and fear that occurred right before the victims died. The 25-second interval also relates to the source of the incident. If the ignition had happened right after the blowout, then static electricity or metal fragments could have sparked the ignition, Koper says. “But because it took so long, it is possible that the gas flooded out and pooled over this whole area and then was ignited, perhaps, by something in the campsite.” Koper’s testimony is thus important in understanding what happened that early morning in New Mexico.

What also makes the investigation of exotic seismic events unique, Koper says, is the fast return time of information. Real-time seismic data are continuously available in an increasing number of areas. After the attacks on the World Trade Center in September, seismic data were immediately available from researchers at Columbia University’s Lamont-Doherty Earth Observatory and at the University of California-Berkeley.

“In the case of September 11, the seismology does not provide much new information beyond all the eyewitness accounts. However, understanding these signals will help us in future events which need analysis,” Wallace says. Emily Brodsky, a seismologist at the University of California-Berkley, adds, “My goal in looking at the data is to determine the relationship between the observed waves and the physical source with an eye toward improving our ability to interpret, and ultimately mitigate, explosive eruptions.”

Lisa M. Pinsker

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