Cascadia's Fault - Jerry Thompson [133]
Now Rogers’ voice was rising. “That’s what we’re talking about, big shaking. It damages a lot of buildings. And then a tsunami comes in on the shore. And we need to be able as a society to deal with that situation.”
CHAPTER 22
The Next Wave: Thinking the Unthinkable
To me the good news is that people living on the edge of North America are finally beginning to respond. Outport communities on the west coast are taking advantage of new flood maps that show how high up the beach Cascadia’s wave is likely to reach, what parts of town will be inundated, and where the safe zones on high ground should be located. Tsunami evacuation routes have been mapped and signs posted. People are going to night classes to learn what they need to know in order to survive. Evacuation drills are being held. And in some cases schools, hospitals, and other vital public buildings are being reinforced or relocated.
Scientists from at least half a dozen universities in the United States and Canada are creating or updating numerical models that use detailed bathymetric maps of the local harbors and offshore terrain to predict much more precisely how far uphill and inland the turbulent muck is likely to travel. They’re doing on a local level what Vasily Titov’s model did on a global scale. Computer simulations of Cascadia’s tsunami have been generated for the city of Victoria and for the fishing village of Ucluelet on the west coast of Vancouver Island, for Cannon Beach and Seaside on the Oregon coast, and dozens of others are in development.
Not every community in harm’s way has a computer model to map the inundation zone. At least not yet. Some towns such as Port Alberni, which was hammered by the Alaska tsunami of 1964, don’t have detailed bathymetric grids to work with because hydrographic survey ships are expensive to operate and government research budgets have been slashed. Rather than wait for public funding to catch up with grim reality, Port Alberni’s emergency planning team took matters into their own hands—literally.
Knowing from experience how waves coming in from the coast can get amplified by the narrow canyon walls of a fjord like the Alberni Inlet, local planners asked the experts at the Pacific Geoscience Centre for their best guess about the height of a seawater pulse coming from Cascadia’s fault. Then they took out a standard topographic map of the downtown core along with a red marking pen.
Bob Harper, the head of emergency planning for the city of Port Alberni at the time, walked me through the exercise. “The best advice that we’ve received so far from the scientists is—because of the funneling effect in the Alberni Inlet—that we can expect somewhere in the twenty-meter range of inundation,” said Harper. “So that’s twenty meters high ... Not twenty meters in, but twenty meters up.”
“That means a sixty-foot wall of water?” I asked, trying to imagine the downtown waterfront.
“Yes,” he said quietly. A technician working with Harper began tracing the contour in bright red ink across the heart of downtown. “There’s a band of residences along the riverside here,” his hand swept across the map following the contour around the harbor. It was clear that most of the central business district, all of the industrial waterfront, the pulp, paper, and lumber mills, would be inundated.
Cascadia’s wave would be larger by far than anything seen in 1964, mainly because this subduction zone—birthplace of the tsunami—is so much closer to home. From the moment the ground begins to shake, places like Ucluelet and Tofino on the west side of Vancouver Island, along with Cannon Beach and Seaside on the Oregon shore and the beaches of Pacific County, Washington, may have as little as fifteen minutes before the first wave makes landfall, with as many as