New tsunami analysis raises threat

SEATTLE – Washington state’s evacuation plans for a tsunami along the coast assume a worst-case wave 30 feet high. But a new analysis based on the Indian Ocean tsunami says a quake off the Northwest coast could generate waves two to three times as big – 65 to 98 feet high.

The new analysis is based on a computer model at the University of Rhode Island.

The results are preliminary, but still troubling, said Stephan Grilli, chairman of the university’s Department of Ocean Engineering.

“It raises a flag,” he told the Seattle Times. “I think revising the hazard assessments would be a wise thing to do.”

Tim Walsh, geologic-hazards manager for the state Department of Natural Resources, is skeptical.

“Sumatra is causing some people to think we could have something worse than what we’re planning for,” Walsh said. “I don’t think so, but I’m willing to listen to the people making these arguments.”

The 600-mile-long Cascadia subduction zone, a geologic fault off the Northwest coast, has generated tsunamis in the past. But Walsh says when it slips, the energy is directed sideways and not up; it probably would not drive waves comparable to the 80-footers that slammed Sumatra a year ago.

State scientists and emergency managers will review the new computer-model results, however.

Vasily Titov, a tsunami modeler for the National Oceanic and Atmospheric Administration in Seattle, said his computer simulations suggest the possibility of waves up to 65 feet in some stretches of the Washington and Oregon coasts.

He said he initially thought the numbers were ridiculously high. Then he went to Banda Aceh, on Sumatra’s north coast.

“If such a huge event could happen there, there is no doubt it could happen here,” he said.