An analysis of geological and oceanographic data from the devastating March 2011 earthquake and tsunami that hit Japan has revealed an acoustic log that scientists can use to predict the occurrence of major tsunamis.
Scientists at Stanford University identified key acoustic characteristics of the 2011 earthquake which indicated it would cause a large tsunami, features which they say can be applied globally to create an effective early warning system for massive tsunamis.
Although various systems can detect undersea earthquakes, they can't reliably tell which will form a tsunami, or predict the size of the wave, according to a report by Stanford. Current tsunami warning systems are typically only able to provide a few minutes of advance warning.
On March 11, 2011 a 9.0 earthquake -- the largest in Japan's history -- struck 43 miles off shore, generating a massive tsunami that hit the coast 30 minutes later. The disaster killed more than 15,800 people and displaced hundreds of thousands.
Researchers at Stanford were able to retroactively analyze the earthquake with models based off known geographic features in the Japan Trench, that accurately predicted the seafloor uplift -- which is directly related to tsunami height -- and sense how the tremors move through the crust and the ocean.
The researchers also identified the specific fault conditions necessary for ruptures to reach the seafloor and create large tsunamis, as well as an acoustic profile of sound waves generated at the onslaught of a massive tsunami.
"We've found that there's a strong correlation between the amplitude of the sound waves and the tsunami wave heights," Eric Dunham, an assistant professor of geophysics at Stanford's School of Earth Sciences, said in a statement.
"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."
Though the telltale characteristics of a major tsunami's acoustic signature might vary depending on the geology of the local environment, the researchers say their model could apply to tsunami-forming fault zones around the world.
"The ideal situation would be to analyze lots of measurements from major events and eventually be able to say, 'this is the signal'," said Jeremy Kozdon, who assisted in analyzing the data while still working at Stanford.
"Fortunately, these catastrophic earthquakes don't happen frequently," he said. But when major tsunamis do occur, their data can be input into computer models in the "hopes of identifying acoustic signatures that indicates whether or not an earthquake has generated a large tsunami."
Their research is published in the journal The Bulletin of the Seismological Society of America.
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