Computer Maps Out West Coast Tsunami

Jan. 23 -- A computer model offers a grim picture of alikely side effect of a major Puget Sound-area earthquake: amassive tidal wave known as a tsunami hitting the sound at thespeed of a jetliner.

"If we get a major event on the Seattle Fault, Puget Sound isgoing to get a major tsunami," said Hal Molfjeld, a scientist atthe National Oceanic and Atmospheric Administration's PacificMarine Environmental Laboratory.

Today a two-day workshop is to open at the NOAA lab,bringing together scientists and emergency-management experts toexamine the risks of a tidal wave and how best to prepare for it.

"We know we're going to get tsunamis," said NOAA's FrankGonzalez. "We just don't know when."

Underwater Surge

Tsunamis are huge pulses of energy caused by quakes orunderwater landslides that can move through the water at 500 mph.Since 1990, 10 major tsunamis in the Pacific have killed more than4,000 people.

Earthquakes are an inevitable part of life in westernWashington, which is crisscrossed by fault lines.

Shunichi Koshimura, a Japanese researcher on loan to the NOAAlab, created a computer map of a tidal wave's progression in PugetSound after a magnitude-7.6 quake on the Seattle Fault, which runsbeneath the city.

Similar to when a large quake struck the Seattle Fault about1,000 years ago, the model shows the southern side of the faultthrusting upward while the northern side drops. That produces a 15-to 20-foot wall of water heading mostly south on Puget Sound.

Due For a Quake

Until recently, scientists thought the Northwest faced littlethreat from tsunamis.

But in the late 1980s, a University of Washington geologistdiscovered evidence of huge quakes and tsunamis in the region. Suchmajor quakes appeared to happen every 300 to 700 years, with themost recent in 1700.