Science: How the tsunami spread
One minute before 8 a.m. on Dec. 26, 2004, a 9.0-magnitude earthquake sent a gigantic tsunami crashing over southeastern Asia, killing hundreds of thousands, ruining billions of dollars in property, and sending the world rushing to the aid of the wave's victims. The effects were felt far and wide, with strange tidal patterns and high waves oceans away from the epicenter.
This week, scientists from the United States, Canada, and Russia report online in the journal Science how the wave traveled around the world, paving the way for tsunami prediction models that might in the future be able to tell where a tsunami will hit and how hard in real time.
The researchers found that near the origin of the tsunami, the direction of the wave is determined by the shape of the tsunami's source. In the case of last year's tsunami, the fault line that created the wave was narrow and very long. As the wave spreads, oceanic ridges–mountain ranges on the ocean floor–act as beams, guiding the waves along their lines under the sea. That, says Vasily Titov, a scientist at the National Oceanic and Atmospheric Administration and one of the researchers on the paper, explains why places like Crescent City, Calif.–not the much closer Hawaiian Islands–had the highest waves on the American coastline. Or why Halifax, Nova Scotia, on Canada's Atlantic coast, had higher waves than the Cocos Islands, off the northwest coast of Australia about 1,000 miles from the epicenter.
Previous tsunamis, says Titov, have not been large enough to register on gauges around the world. But since this one was so enormous, it allowed the scientists to take data from all over and see where the wave went.
"It was known before that the underwater topography influences wave propagation," says Titov. "But we saw with this tsunami that was the main factor."
Titov said that the scientists hoped to use this information to better predict where a tsunami will hit and how hard much more quickly the next time around.
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