22 December 2015
Earthquake detectors pick up wartime explosions and helicopters
Military history is hidden in the squiggles of a seismogram. During the Iraq war, earthquake-monitoring instruments at Baghdad's seismic observatory also recorded wartime activity including car bombs, weapon rounds and improvised explosives.
"Having a seismometer right in the middle of Baghdad, right in the midst of all this fighting – it turned out we had this marvellous opportunity for forensic seismology," says Michael Wysession at Washington University in St Louis, Missouri. "This was just luck, in a sense."
Wysession and his colleagues looked at the data for traces of a big event on 10 October 2006, when rounds fired into an ammunition supply point set off a chain of explosions 7 kilometres from the observatory.
They detected not just this "cook-off", but also evidence of other nearby reported military activity. There were unique seismic signatures for each type of weapon. And vibrations from heavy air traffic were clear enough that they could discern the type and speed of helicopters flying past.
Such information could be useful for gathering military intelligence, says Stephen Arrowsmith at Sandia National Laboratories in Albuquerque, New Mexico.
"What makes this study very unique and interesting to me is that it's an actual set of measurements from actual military operations," Arrowsmith says. That makes the data harder to study and verify, but valuable for learning how to identify unknown events. "It could be quite useful as a tool to characterize what's going on in this type of environment."
Journal reference: Bulletin of the Seismological Society of America, DOI: 10.1785/0120140187
Image credit: Baz Ratner/Reuters