GPS satellites may be able to detect earthquakes before they happen

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Predicting earthquakes is impossible.

When it comes to knowing when an earthquake will strike, the crucial missing piece of the puzzle is what seismologists call the precursor: a telltale fingerprint of an earthquake that arrives before the big event. To date, no one has found reliable precursors; Not many scientists think they’ll ever find one.

But two researchers may have made a breakthrough in the search for precursors. If they’re right, earthquakes could make their presence known through GPS measurements, several hours before their main events.

“Conceptually, that tells you that it is possible to do this. This is a big step,” thought Quentin Plettieri, a seismologist at the Research Institute for Development and the University of Côte d’Azur in France.

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Bletery and colleague Jean-Mathieu Nocquet turned to a dataset maintained by the University of Nevada at Reno. Every five minutes, thousands of stations around the world record their GPS positions. These observations allow scientists to detect even very slight movements. If the Earth moves, Bletery and Nocquet can see it in the GPS data.

By identifying GPS stations located around the known locations of earthquakes of magnitude 7.0 or higher, Bletery and Nocquet studied the recorded locations of those stations—and how they changed—in the 48 hours before the earthquake in question. They calculated how well the actual motion matched the motion they expected each earthquake to cause.

The researchers found that in the last two hours before an earthquake, the ground’s movement often began to align with the expected movement. This alignment appears to intensify as the time of the earthquake approaches. Although this pattern is slight, it was not generally seen when Bletery and Nocquet examined randomly selected windows for two hours that had mostly no earthquakes.

Artist’s illustration of a GPS satellite above Earth. (Image credit: BlackJack3D/Getty Images)

Thus, the motion in these last two hours may contain the precursors that seismologists have long sought. But even with this knowledge, seismologists are far from turning it into a way to predict earthquakes. That’s because today’s tools are not good enough to detect this movement before it happens. Bletery says existing equipment would need to be about 50 times more sensitive in order to detect a single earthquake precursor.

“This is a huge technology gap,” says Pelletri. “We don’t have the technology yet to do that.” Adding more GPS stations might help, and Bletery expects scientists to do just that, but it won’t be enough on its own.

Still, Bletery thinks it’s a sign of progress that might interest scientists. For example, their discovery provides evidence that earthquakes are not chaotic, but rather instantaneous events caused by suddenly moving faults. Instead, the two-hour preview suggests that earthquakes may have precursor elements that could give up before they happen.

Moreover, their findings opened up other questions. The largest earthquake Bletery and Nocquet studied was the 9.0-magnitude Tohoku-Oki earthquake, which triggered a devastating tsunami off Japan’s eastern coast in 2011. When they checked GPS data along the Japanese coast, they found that the motions appeared identical more than two hours before the earthquake: in a cycle that seemed to repeat every 3.6 hours or so. What, if any, caused this circuit remains a mystery.

The research was published in the journal Science.

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