Shallow Water Provides Clue to Destructive Tsunami Power

For the first time a team of mathematicians have monitored the ocean waves in order to explain why tsunami causes havoc and destruction.

The two mathematicians from the University of Colorado Boulder applied mathematicians have discovered the interacting X- and Y-shaped ocean waves that explain why some tsunamis cause havoc.

This study was conducted by Professor Mark Ablowitz and doctoral student Douglas Baldwin.

The two repeatedly observed the wave interactions in ankle deep water at both Nuevo Vallarta, Mexico and Venice Beach, Calif. in the Pacific Ocean, interactions that were thought to be very rare but which actually happen every day near low tide. 

On monitoring these waves, they noticed single straight waves interacting with each other to form X- Y shaped waves as well as more complex wave structure. It was all predicted by mathematical equations.

When most ocean waves collide, the "interaction height" is the sum of the incoming wave heights, said Baldwin. "But the wave heights that we saw from such interactions were much taller, indicating that they are what we call nonlinear," he said.

The considered the satellite observations of the 2011 tsunami generated by the devastating earthquake that struck Japan. They noticed an X-shaped wave that was created by the merger of two large waves.

 "This significantly increased the destructive power of the event," said Ablowitz. "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 nonlinearity."

"Unlike most new physics, you can see these interactions without expensive equipment or years of training," said Ablowitz. "A person just needs to go to a flat beach, preferably near a jetty, within a few hours of low tide and know what to look for."

The details of the study were published in this month journal Physical Review E.

"I don't think there is anything more enjoyable in science than discovering something by chance, predicting something you haven't seen, and then actually seeing what you predicted," said Baldwin.