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Hydro International -
NASA and Ohio State University, USA, researchers have discovered the major tsunami generated by the March 2011 Tohoku-Oki quake centred off northeastern Japan was a long-hypothesized "merging tsunami."
The tsunami doubled in intensity over rugged ocean ridges, amplifying its destructive power at landfall.
Data from NASA and European radar satellites captured at least two wave fronts that day. The fronts merged to form a single, double-high wave far out at sea.
This wave was capable of travelling long distances without losing power. Ocean ridges and undersea mountain chains pushed the waves together along certain directions from the tsunami's origin.
The discovery helps explain how tsunamis can cross ocean basins to cause massive destruction at some locations while leaving others unscathed.
The data raise hope that scientists may be able to improve tsunami forecasts.
Research scientist Y. Tony Song of NASA's Jet Propulsion Laboratory in Pasadena, CA, and professor C.K. Shum of The Ohio State University discussed the data and simulations that enabled them to piece the story together at a media briefing Monday, 5th December 2011 at the American Geophysical Union meeting in San Francisco.
It was a one in 10 million chance that we were able to observe this double wave with satellites, according to Song. He is the principal investigator in the NASA-funded study.
He continues saying that researchers have suspected for decades that such 'merging tsunamis' might have been responsible for the 1960 Chilean tsunami that killed about 200 people in Japan and Hawaii, but nobody had definitively observed a merging tsunami until now.
A NASA-French Space Agency satellite altimeter happened to be in the right place at the right time to capture the double wave and verify its existence.
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