Fenglin Niu of Rice University, Paul Silver of the Carnegie Institution and Tom Daley of Lawrence Berkeley National Laboratory gathered measurements from sensors in deep wells at the San Andreas fault In California.
by Zack Beauchamp
We have satellites to detect hurricanes, rainfall projections to predict floods and even tsunami detectors. All provide precious time to evacuate before the worst happens.
But despite more than 30 years of research, there is still no accurate earthquake detector, as China heartbreakingly found out earlier this year. The Sichuan Basin quake killed over 60,000 people.
But there is new hope: a team of researchers working in the Parkfield region of the San Andreas Fault in California believe that a novel approach for measuring seismic waves may hold the key to developing a practical, early-warning earthquake detector.
The new method looks for subtle signs of distress in the earth that can be picked up much further in advance than large changes that precede earthquakes by just seconds.
According to Paul Silver, a seismologist at the Carnegie Institution of Washington, those subtle signs are seismic waves generated by stress in the earth. Silver and his colleagues measured these waves by putting sensors in two holes, each a kilometer deep, near each other at the Parkfield site.
"We used a specially designed system to generate and record seismic waves before, during and after two earthquakes on the San Andreas Fault. It's been shown in the lab that the speed of seismic waves varies with the level of stress, due to the effect on the opening and closing of cracks. So measurements of changes in wave speed should, in principle, constitute a 'stress meter' that could provide an indication of an imminent earthquake," Silver said.
He added: "Researchers have been trying to precisely and continuously measure these velocity changes for decades, but it has been possible only recently, with improved technology, to obtain the necessary precision and reliability."
What the researchers found was that the signals changed dramatically 10 hours before a magnitude 3 quake and two hours before a magnitude one quake.
Silver is quick to caution that the link between stress and earthquakes is not yet proven, and that he and his colleagues are still ten to twenty years from developing a practical earthquake detector from their current research on seismic waves.
However, based on some initial successes, he says research in this area "is a very promising field" for the eventual development of an earthquake detector.
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