December 28, 2004
KATU TV News — Portland

SOUTH BEACH, Ore. - Even the good news would be awful if the Big One hits off the Oregon or Washington coast.

Geologist Bill Chadwick of the Hatfield Marine Science Visitors Center says an earthquake far at sea could give coastal residents and visitors an hour or two to get to higher ground.

But if it happens in the Cascadian Subduction Zone, which varies from 32 to 70 miles off the coast between Vancouver Island, Canada, and Crescent City, Calif., the time could be only 10 to 20 minutes. In either case property damage alone would be horrendous.

"For the local ones, you just have to get to higher ground," Chadwick said. "Basically, the earthquake is your warning."

He said information and preparation are improving, but if it happened now "it would be a really horrible thing." It wouldn't be the first time.

Based on evidence such as tsunami debris and drowned forests, scientists believe there was an earthquake estimated at 9.0 intensity off this coast around the year 1700 and resulting tsunamis that rearranged the Oregon Coast and reached Japanese fishing villages.

A 1964 Alaska earthquake, with an intensity of 8.3, did major damage in Seaside and Crescent City, Calif. and affected other areas. Four campers died at Beverly Beach.

Scientists and geologists think a powerful offshore earthquake 2,000 years ago advanced the coastline as much as 7 feet, submerging coastal forests.

In Agate Beach and Neskowin, ancient stumps from such events sometimes poke up through the sand.

"It's not a very regular thing," Chadwick said. "The dates I've heard are every 300 to 600 years. We are sort of at the beginning of the window when it could happen," he added. "It's a really low probability, but if it happened, it would be really bad."

Although the main damage would be to low-lying areas such as Neskowin, Waldport, Pacific City, Seaside and South Beach, all the beaches, bays and inlets could be affected.

The Hatfield Marine Science Visitors Center itself sits in a tsunami hazard zone on Yaquina Bay.

The maximum "run up," or height affected, would be 100 feet. Waves could reach 18 to 52 feet in height and could last up to 10 hours, Chadwick said.

People would need to stay on higher ground for hours because of possible other tidal waves.

The amount of damage likely would be staggering, he said. "Tsunamis can do an incredible amount of damage, because the water rushes in and it has a huge amount of power," Chadwick said.

The Cascadian Subduction Zone is one of the largest active fault zones in North America, according to the Hatfield center.

Some Oregon coastal communities have emergency measures in place.

Ray Weldon, geology professor at the University of Oregon and an expert on undersea earthquakes and resulting sunamis, said casual visitors to the beach may face a chance of one in 10,000 of encountering a destructive wave of any size, but that the odds go up to about one-in-four for life-long residents.

"It's not something people should be worried about," Weldon said. "But it is something everybody should be prepared for."

"The Oregon Coast is pretty rugged there are few places that are far from high ground," he said.

Towns such as Coos Bay-North Bend, Reedsport, Florence, Yachats, Waldport and Newport have brochures that describe how the community will attempt to alert people, evacuation routes and where to get emergency information.

Some plan to use a three-minute siren blast to alert residents. Signs along the coast alert people as they enter and leave tsunami hazard zones.

The weekend tragedy that killed at least 52,000 people in Asia, the Pacific and Africa may boost an awareness level that has been low.

"I teach a class twice a year about what to do the first 48 to 72 hours after an earthquake, and I have a difficult time filling the class up," said David Davis, a volunteer firefighter and coordinator of the community emergency response team for the Siuslaw Valley Fire & Rescue Department.

(Copyright 2004 by The Associated Press. All Rights Reserved.)

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