‘Merging Tsunami’ Doubled Destructive Power Along Japanese Coast

A detailed analysis of satellite data shows that the devastating tsunami that struck the coast of northeastern Japan last March doubled in intensity because two wave fronts generated by an undersea earthquake merged before making landfall. Researchers from NASA and Ohio State University discovered that three satellites — all carrying radar altimeters that can measure sea level changes to within a few centimeters — passed over the tsunami waves as they formed last March 11. The rare coverage by several satellites enabled the researchers to determine that ocean ridges and undersea mountain chains helped create two large tsunami waves that merged into one enormous wave as the tsunami bore down on the coast. Such a huge wave was able to travel long distances without losing power, according to the researchers, who presented their findings at the American Geophysical Union meeting in San Francisco.