NW coast has Tsunami warning system in place
Tuesday, December 28, 2004 7:40 AM PST
By Andre Stepankowsky
Printable version
E-mail this articleIt will happen here --- someday.
And when it does, don't stop and wait for a warning. If you're anywhere near the Oregon or Washington coasts, just head for whatever high ground you can find.
The tsunami that follows the next great earthquake off the Northwest Coast could come charging inland within 15 to 20 minutes.
"If you feel the ground shake, you need to move," said Stephanie Fritts, emergency management director for Pacific County, which has established a series of tsunami evacuation routes and sites across the Long Beach Peninsula.
"You will not have time to get places. A (locally generated) tsunami comes ashore in 15 to 20 minutes. We ask people to find the closest, highest places they have. That might be a second story of a house," Fritts said.
Unlike the regions around the Indian Ocean and Southeast Asia, the West Coast of North America has a tsunami warning system in place.
The West Coast/Alaska Tsunami Warning Center, based in Palmer, Alaska, uses hundreds of earthquake and sea-level gauges to locate and size major earthquakes in the Pacific Basin, determine their tsunami potential, predict tsunami arrival times and, when possible, runup on the coast. Its purpose is to issue warnings for the coastal populations of California, Oregon, Washington, British Columbia and Alaska.
The system can give timely warnings about tsunamis generated in distant places. However, it might not be of much use for tsunamis generated just off the Northwest Coast, in this region's back yard, so to speak.
The shock waves generated by undersea earthquakes travel at the speeds of jetliners, slowing down as they approach shore and heaving waters far inland. Studies have shown deposits of tsunami sand waves far inland of the town of Long Beach, for example.
Contrary to what most people envision, a tsunami "wave" is more like a rush of water that surges inland, not a wall of water that crushes everything in its path. The biggest danger they pose is swamping people with debris or dragging humans out to sea when they recede. It's possible to stay out of harm's way by taking refuge on a higher building, even if the lower floors are inundated.
Sunday's earthquake off the southwest coast of Indonesia occurred on a 600-mile underwater frontier where two clashing slabs of the earth's crust have been crunching together, building up incredible strain over decades or centuries.
It's parallel to what seismologists say will occur when the 700-mile long "Cascadia subduction zone" between the Juan de Fuca and North American plate ruptures, creating the long-awaited "big one" that scientists say is inevitable in this region.
The last time that happened was on Jan. 26, 1700. The earthquake, estimated at about magnitude 9, jolted the sea floor from Vancouver Island to Northern California. The shock wave stirred up tsunamis that swamped Indian villages along the Pacific Coast and communities across the Pacific Ocean in Japan.
Sunday's Indonesia earthquake offers are rare glimpse into what the Northwest will experience again one day.
"The parallels are incredible," Brian Atwater, a U.S. Geological Survey geologist who helped document the last great Cascadia earthquake and many others that have occurred over the past 10,000 years, told The Associated Press.
Last weekend's tragedy in the Indian Basin "validates some of the work that we've been doing since the early 1990s. It makes me feel gratified in the fact that we have a tsunami warning system in place," said Fritts, the Pacific County emergency management director.
Fritts said the Indonesia quake "deeply saddens me." At the same time, however, "it gives us a little touch with reality in what the impacts of this could truly be."
She said that public surveys in Pacific County show that most coastal residents are aware of the dangers that earthquake and tsunamis pose to their communities. She gets frequent calls from people there asking for information.
"I do believe that most of our residents area aware of the danger."
Official evacuation points in Pacific County*.
• North peninsula: Surfside Golf Court and Douglas Drive.
• Middle peninsula: U street, a long north-south route in the middle of the peninsula, which is only a mile wide.
• South Peninsula: School hill in Ilwaco; Cape Disappointment State Park.
• Chinook area: Fort Columbia State Park.
* Officials don't expect any significant tsunami impacts up the Columbia River east of Puget Island. However, communities within the Interstate 5 corridor are vulnerable to extensive damage from the Cascade "subduction zone" earthquake.
Andre Stepankowsky is the city editor of The Daily News. He wrote the script for "Cascadia: The Hidden Fire," a documentary film about the region's vulnerability to earthquakes.
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