Understanding Earthquake Lights

Electrical spikes of 100 volts or more can result when a crack opens and closes in bed of powder under stress in a laboratory-scale experiment. (Image courtesy of Troy Shinbrot, Rutgers University.)
Electrical spikes of 100 volts or more can result when a crack opens and closes in bed of powder under stress in a laboratory-scale experiment. (Image courtesy of Troy Shinbrot, Rutgers University.)

Researchers appear to be on the brink of an explanation for lightning strikes that sometimes precede earthquakes. Unlike normal lightning, which results from the buildup of charged regions in clouds, recent experiments in labs suggest that the so-called “earthquake lights” instead may originate from the shifting of granular materials in the ground around a geological fault. The research will be presented March 6 at the 2014 APS March Meeting in Denver, CO.

Troy Shinbrot (Rutgers University) and colleagues have looked at electrical signals in three different types of granular systems that exhibit the same sorts of flow, jamming and slip events that occur in the earthquake zones, as well as in granular materials involved in various industrial processes. These different systems all developed electrical charges at levels that cannot be explained with known physical mechanisms.

“It is quite surprising to us,” said Shinbrot, “to get hundreds of volts by the very low stress, small scale experiments, essentially consisting of tipping a bed of flour.”

Shinbrot and his collaborators are using their experiments to develop a new theory that they hope will explain charging in granular material, potentially leading to a way to pinpoint the epicenter of an earthquake. A more pragmatic outcome may be the potential to use electrical measurements to monitor the production of ceramics, pharmaceuticals, and other products that require uniform, high quality powder blends.

S17.00007: Unexplained voltage signals from granular materials. Thursday, March 6, 9:12 AM, Room 402

ABSTRACT: http://meetings.aps.org/Meeting/MAR14/Event/214444

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