U.S. scientists have made what could be an important breakthrough in the science of earthquake prediction.
Image: Earthquake damage in Bei Chuan. Credit: Wikipedia
A study appearing in this week's Nature journal says researchers have detected stress-induced changes in the Earth's crust some hours prior to two minor quakes occurring on the San Andreas Fault in California. Current earthquake-detecting systems are limited to warnings amounting to just seconds.
"We are encouraged," said seismologist Dr. Paul Silver of the Carnegie Institution of Washington's Department of Terrestrial Magnetism in Washington, D.C., a co-author of the paper. "It's a very intriguing signal."
The team has said, though long-term earthquake prediction is not practical at present, the discovery does show such technology may soon become available and bring with it the potential to save millions of lives.
"If you had 10 hours' warning, from a practical point of view, you could evacuate populations, you could certainly get people out of buildings, you could get the fire department ready," said Dr. Silver to the BBC. "Hurricane [warnings] give you an idea of what could be done," he added.
Researchers, which included teams from Rice University and the Lawrence Berkeley National Laboratory, were able to detect two signals prior to an earthquake along the fault line. The first occurred some two hours before, the second around ten hours prior to the quake. The scientists conducted their experiments at Parkfield, a tiny rural town halfway between Los Angeles and San Francisco.
"What we're looking for are changes in the velocity that would correspond to changes in stress, and it has been hypothesised that such stress changes would precede seismic events and could be used as precursors," said Dr. Silver, explaining that wave speed varies with stress due to cracks opening and closing in the rock.
"For a long time, people have been trying to do this. I think right now the technology has gotten better so we can measure this change more accurately."
The team has said it will coordinate its ongoing research with seismologists from China and Japan.
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