Getting Ready for the Big One
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The little stick figure running uphill on the blue tsunami warning signs has Pat Corcoran concerned.
“The signs make people aware that they’re in a tsunami zone,” he says. “But much work needs to be done to transform their general awareness into a deeper understanding and, most importantly, behavior change.”
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OSU's Pat Corcoran is a partner in the National Oceanic and Atmospheric Association's Coastal Storms Project, which recently deployed a new meteorological buoy off the north coast to help provide early warning of oncoming storms. Photo: Pat Corcoran |
Corcoran, a coastal hazards educator for Oregon State University Extension Service in Astoria, wants people to prepare for the Big One—the catastrophic tsunami that experts say is certain to strike the Pacific coast again, sooner or later. He’s taking his message everywhere people will listen: schools, city halls, even the county fair. The tragedy of the tsunami that struck south Asia on the day after Christmas 2004 got people’s attention, Corcoran says. But even now, most of us know only enough about tsunamis to be scared of them. “One of my biggest challenges,” he says, “is to help people narrow down what to worry about and keep focused on what’s important.”
He strips information down to the essentials. “There are the three things you need to know about tsunamis,” he says to his audiences. “First: learn where the safe and the dangerous zones are where you live, work, and play. Second: understand the difference between a near event and a distant event, because that makes a crucial difference in how much time you have to get out of danger. Third: know how to get in touch with your family members under each scenario. Create a communication plan now. You don’t want to go back into a hazardous area in search of a family member who’s already safe on high ground.”
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Warning signs that instruct coastal residents and visitors of tsunami hazards were designed by the OSU Extension Service and are now used internationally. iStock photo |
Tsunamis, once erroneously called tidal waves, have nothing to do with tides. They are lateral movements of the ocean resulting from undersea grindings of the earth’s crustal plates. Corcoran offers this homespun analogy: “When your dog laps water from his bowl, he’s making waves. When he kicks the bowl across the floor and it slams into the refrigerator and water spills over the side, that’s a tsunami.” Even small tsunamis are “incredibly powerful,” he says.
Tsunamis are a frequent visitor to the Pacific Coast, geologically speaking. The Cascadia Subduction Zone, the large offshore fault line, has produced 23 earthquakes in the past 10,000 years, and at least 16 of them have produced huge tsunamis, according to research conducted by OSU marine geologist Chris Goldfinger. The last big earthquake from the Cascadia zone produced a tsunami that slammed into the Pacific Coast on January 26, 1700. We know the date because of records kept in Japan, which also experienced the tsunami. Further evidence comes from carbon-dating submerged forests in Oregon and from layers of sediment deposited in undersea canyons by large earthquakes.
These quakes have occurred in clusters of four or five roughly every 300 to 400 years, followed by a quiet period of 800 to 1,000 years. Seismologists speculate that there may be another quake coming in this current cluster. That translates to a 15 to 20 percent chance that another big quake and tsunami will happen in the next 50 years.
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This submerged "ghost forest" near the mouth of the Copalis River in Washington is evidence of a massive tsunami that hit the coast in 1700. Photo: Brian Atwater. USGS, in The Orphan Tsunami of 1700. |
All tsunamis are not created equal. A distant earthquake may produce a tsunami, but people will have time to get out of danger. “If you hear about a tsunami warning on TV, or if you hear a siren, it’s a distant event,” Corcoran says. The most likely location of a distant event is Alaska, and it takes three to four hours for a tsunami to make its way from there to Oregon. “For those who live in inundation zones, I suggest you make friends in high places. You need to evacuate those zones, but you have time to make your way in an orderly fashion. Stay out of inundation zones for 10 hours or until you’re instructed to return by emergency officials.”
On the other hand, if it’s a local Cascadian earthquake, you’ll know it. “Make no mistake: the Big One will be obvious,” Corcoran says. Duck, cover your head from falling debris, and hold on until the shaking stops. Then, if you are in an inundation zone, run immediately for high ground. “You’ll have approximately 25 minutes to get to 50 or 60 feet above sea level,” he says. Don’t expect to drive your car to safety after the Big One. The huge earthquake that generates the local tsunami will topple power lines and will likely destroy bridges and phone lines.
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At OSU's O.H. Hinsdale Wave Research Laboratory, researchers in the College of Engineering can model the impact and inundation of tsunamis on coastal communities. Photo: OSU O.H. Hinsdale Wave Research Lab |
Corcoran’s workshops have sparked serious conversation. Attending one community workshop was the director of several group homes for developmentally disabled people. Some of the homes were located in the inundation zone along the north coast. The director got Corcoran together with group home staff, “and we talked frankly about the implications. One person told me, ‘I can’t get my clients to walk 20 minutes on a good day, let alone after they’ve had a very frightening experience.’ What was the alternative, she wanted to know. Hand out life preservers?”
From that conversation came a plan: the company that owned the group homes would begin selling the ones in the inundation zone and buying others on higher ground, moving the most vulnerable clients out of danger first. “What started out as a dismal conversation,” Corcoran says, “turned into a plan for positive change.”
Corcoran acknowledges that when a hazard is dangerous but hard to predict, it’s easier for people to ignore it. “We’re wired to react to immediate threats, like a lion jumping out of the bushes,” Corcoran says. “But I hope that we’ve evolved enough to prepare for an event that we know to be inevitable.”