Hugh Pickens writes "The magnitude-9.0 Tohoku-Oki temblor, the fifth-most powerful quake ever recorded, triggered a tsunami that doubled in intensity over rugged ocean ridges, amplifying its destructive power at landfall, as seen in data from NASA and European radar satellites that captured at least two wave fronts that day, which merged to form a single, double-high wave far out at sea. This wave was capable of traveling long distances without losing power. Ocean ridges and undersea mountain chains pushed the waves together along certain directions from the tsunami's origin. 'It was a one-in-10-million chance that we were able to observe this double wave with satellites,' says study team member Y. Tony Song. '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.' The study suggests scientists may be able to create maps that take into account all undersea topography, even sub-sea ridges and mountains far from shore to help scientists improve tsunami forecasts."