Researchers from NASA and the Ohio State University said satellites captured not just one wave front that day, but at least two -- which merged to form a single double-high wave far out at sea capable of traveling long distances without losing its power, an OSU release said Monday.
Ocean ridges and undersea mountain chains pushed the waves together, they said.
"It was a one-in-10-million chance that we were able to observe this double wave with satellites," Y. Tony Song, a research scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif., said.
"Researchers have suspected for decades that such 'merging tsunamis' might have been responsible for the 1960 Chilean tsunami that killed many in Japan and Hawaii, but nobody had definitively observed a merging tsunami until now," he said.
Ridges and undersea mountain chains on the ocean floor deflected parts of the initial tsunami wave to form independent jets shooting off in different directions, Song said.
"Tools based on this research could help officials forecast the potential for tsunami jets to merge," he said. "This, in turn, could lead to more accurate coastal tsunami hazard maps to protect communities and critical infrastructure."