An earthquake's sonic 'signature' could warn of impending tsunami

U.S. scientists say the acoustics of an earthquake can indicate its potential to cause a tsunami, a finding that could lead to a tsunami early warning system. Researchers at Stanford University say they have identified key acoustic characteristics of the 2011 Japan earthquake that strongly suggested it would cause a large tsunami, and that the sound waves in the ocean produced by the earthquake probably reached land tens of minutes before the tsunami. If correctly interpreted, they could have offered a warning that a large tsunami was on the way, they said. Various systems can detect undersea earthquakes but can't reliably tell which will form a tsunami, or predict the size of the wave, and while there are ocean-based devices that can sense an oncoming tsunami they typically provide only a few minutes of advance warning, the researchers said. Since the sound from a seismic event can reach land well before the wave itself, the researchers suggest identifying the specific acoustic signature of tsunami-generating earthquakes could lead to a faster-acting warning system for massive tsunamis. "We've found that there's a strong correlation between the amplitude of the sound waves and the tsunami wave heights," geophysics Professor Eric Dunham said in a Stanford release Thursday. "Sound waves propagate through water 10 times faster than the tsunami waves, so we can have knowledge of what's happening a hundred miles offshore within minutes of an earthquake occurring. We could know whether a tsunami is coming, how large it will be and when it will arrive." While the findings could apply to tsunami-forming fault zones around the world, the researchers acknowledge the characteristics of telltale acoustic signatures might vary depending on the geology of the local environment. "The ideal situation would be to analyze lots of measurements from major events and eventually be able to say, 'this is the signal,'" researcher Jeremy Kozdon said.