Wave action in tsunamis studied

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BOULDER, Colo., Sept. 19 (UPI) -- The way that waves interact in shallow water may help explain why some tsunamis become more destructive than others, U.S. mathematicians say.

Two University of Colorado Boulder applied mathematicians report the discovery of ocean waves created when two straight waves interact may help explain why some tsunamis are able to wreak so much havoc.

Professor Mark Ablowitz and doctoral student Douglas Baldwin repeatedly observed such wave creation in which single, straight waves interacted with each other to form X- and Y-shaped waves as well as more complex wave structures, all predicted by mathematical equations.

When most ocean waves collide, the "interaction height" is the sum of the incoming wave heights, Baldwin said.

"But the wave heights that we saw from such interactions were much taller, indicating that they are what we call non-linear," he said.

Satellite observations of the 2011 tsunami that struck Japan indicate there was an X-shaped wave created by the merger of two large waves.

"This significantly increased the destructive power of the event," Ablowitz said. "If the interaction had happened at a much greater distance from shore, the devastation could have been even worse as the amplitude could have been even larger. Not every tsunami is strengthened by interacting waves, but when they do intersect there can be a powerful multiplier because of the non linearity."