UH prof says he can predict tsunami size

A University of Hawaii professor's new tsunami forecasting method could be the next big thing in disaster preparedness in Hawaii.

Ocean engineering professor Kwok Fai Cheung says using measurements from tide gauges near an earthquake site -- along with deep-ocean buoys -- will better predict the size of a tsunami.

Cheung thinks the model will work particularly well for earthquakes with large fault areas or slow ruptures, which are hard to deduce from measuring the earth's movement.

Cheung and Alejandro Sanchez, a former graduate student, tested their model with an analysis of the 1995 Antofagasta-Chile tsunami, they said in a paper published last month in the academic journal Geophysical Research Letters.

That "hindcast" accuracy, when compared with actual tsunami wave sizes that reached Hawaii from that event, shows the model's effectiveness, Cheung told the Star-Bulletin yesterday.

Pacific Tsunami Warning Center geophysicist Gerard Fryer called Cheung's model "a promising new technique."

The method "may be a little ways away" for use in forecasting, Fryer said. "But I think it's going to help significantly in figuring out how big a tsunami is going to be."

"Right now we can do a great a job of telling you when the tsunami is going to arrive, but we don't know how big it's going to be," Fryer said.

However, a recent improvement predicting the size of Hawaii-bound tsunamis was demonstrated with the Aug. 15 earthquake off the coast of Peru, Fryer said.

That earthquake was only the second time the Seattle-based Pacific Marine Environment Laboratory used data from deep-ocean buoys coupled with computer modeling.

The Seattle lab's "calculations for Hilo were so good that it will certainly make us more comfortable in using them" in the future, Fryer said.

The lab in Seattle and the Pacific Tsunami Warning Center in Ewa Beach are both part of the National Oceanic and Atmospheric Administration.

Cheung said the recent analysis of South American tide gauge data is the last in a series of three papers he has published since 2001 about tsunami warning models. Earlier papers focused on the other two areas from which tsunamis that could hit Hawaii would come: Japan and Alaska.

The bottom line is better predictions for Hawaii, Fryer said.

The last Hawaii coastal evacuation for a tsunami was in 1994, Fryer noted. The accuracy of tsunami predictions has increased so much since then, he said, that the next time the center calls for an evacuation, "people need to take it seriously."