Cascadia's Fault

by Jerry Thompson

  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 eight or ten more en route behind it. And so the obvious question arises: what could or should a person standing on the beach do to survive? The logical answer is to head for higher ground. And do it right away.

  I gave my stopwatch to Patrick Corcoran, who strapped it on his wrist and got ready to run. He stood only a few steps away from the wide, sandy beach at the base of the Lewis and Clark statue in the traffic circle at the western terminus of Broadway, the main drag in Seaside, Oregon. Young and fit, probably in his late thirties, Corcoran is a surfer by choice and an employee of Oregon State University by profession. As a “hazards outreach” specialist, he helps people along the coast plan for and come to terms with some of the realities of life on the edge—things like major winter storms, and getting ready for “the Big One” from Cascadia’s fault.

  Corcoran is demonstrating the official evacuation route, which begins at the beach promenade and follows Broadway, the main east–west business corridor, all the way across the downtown core to higher ground on the east side of town. As I give Corcoran the nod, he clicks the stopwatch and starts running.

  In a real emergency, running or walking would probably be the only way to get out of town fast. Previous experience with tsunami false alarms in Seaside had already taught local residents that vehicle traffic hits gridlock almost immediately. It was a busy summer day so the sidewalk was crowded with shoppers and tourists out for a stroll. Corcoran jogged at a brisk pace, zigzagging through the throng.

  The Pacific coastline here runs almost exactly north–south, so to get away from the ocean on the west side you have to move toward the first rank of low hills in the Coast Range mountains on the east. The city of Seaside is built on the wide, flat delta of the Necanicum River, so anyone trying to outrun a tsunami would have to hustle to get across the two bridges that span branches of the river, hoping the earthquake and the incoming tsunami had not already knocked the concrete decks off their pilings.

  By the time Corcoran got past the river and started uphill on a winding switchback road, he was breaking a sweat and breathing hard. He had covered more than twenty city blocks without gaining any altitude. Now the road started to climb steeply. He already knew from studying the map contours exactly which house he had to reach in order to get himself at least fifty feet (15 m) above sea level and presumably beyond the reach of the biggest waves likely to come from Cascadia’s subduction zone.

  When he crossed the imaginary finish line, he stopped and clicked the watch again. “So, seven minutes and thirty-three seconds,” he huffed. “Not too bad, but it was a hard run.” On a nice sunny day under ideal conditions, he certainly would have made it to high ground in plenty of time. But what if the earthquake happened on a stormy winter’s night? Powerlines and trees would be down and all kinds of obstacles would be in the way.

  And what about those not as young or physically fit as Patrick Corcoran? The likelihood that the vast majority of people could make that run before the first tsunami surge hit the beach seemed pretty slim to me. For those who hung around to watch the incoming waves, mesmerized by the spectacle as so many were on the beaches of Sumatra and Thailand, the chances of survival would be even less.

  Corcoran has a set of simple guidelines he explains to anyone who will listen. Rule number one: if you’re anywhere near the coast in a subduction zone and you feel the earth begin to shake, start moving to higher ground as soon as the shaking stops, or sooner if you can. Rule number two: if you’re living in or visiting a coastal earthquake zone you should already know where the high, safe ground is and how to get there. Grab a map, study the evacuation routes, and always have a sense of where you are. Rule number three: don’t wait for a warning siren because there probably won’t be one. Your only warning will be the violent shaking of the ground, so don’t wait for someone in authority to tell you to run. Rule number four: if you stand there long enough to see the incoming tsunami, there’s almost no chance you’ll outrun it.

  These are the kinds of things Corcoran recites when he does his outreach sessions. “When I came here in 2003 for the Coastal Storms Program,” he begins, “it was all about severe winter storms and flooding and those kind of more chronic or constantly occurring events. Then the 2004 Sumatran earthquake and tsunamis occurred, and while my focus was on storms, I had to ask myself as a coastal hazards agent, is this [tsunami threat] something that I should be paying attention to? And so I asked myself three questions: One, is it likely? Two, would it be bad? And three, can education do anything to improve the situation?”

  In a heartbeat he answers his own questions: “Yes, yes, and Lord, I hope so. Yes it is likely. Yes it would be very bad. And education will, hopefully, go a long way towards improving the odds for most people.”

  The first thing to know, according to Patrick Corcoran, is that if you hear a warning siren you shouldn’t panic. It probably means there has been a distant temblor in Japan, Alaska, or Chile. “So if you heard a siren, or understood a tsunami was coming, and you didn’t feel the earthquake, Alaska is the closest place it’s going to be and that’s three and a half to four hours away,” says Corcoran. “So the good news is—you have time before a small and not so bad tsunami comes.”

  If it’s a seismic jolt closer to home, the Big One from Cascadia’s fault, the sirens won’t have time to go off before the first wave gets here. That’s because NOAA’s warning buoys are anchored farther out in the Pacific—beyond the Cascadia Subduction Zone—in order to provide plenty of warning time for those long-distance waves from Japan, Alaska, and elsewhere. Cascadia’s fault, being much closer to the shoreline of North America, will send out waves both east- and westbound. And the eastbound waves will hit the beaches of California, Oregon, Washington, and British Columbia at the same time as or even before the westbound waves hit the warning buoys and trip the alarm. Until this chink in the armor of the tsunami warning system is dealt with by some newer generation of detectors closer to shore, the only real warning anyone in Cascadia will have is the violent shaking of the earth.

  Corcoran begins to distil the to-do list. The first thing to figure out is whether the quake and tsunami are from far away or closer to home. Did you feel the earth move? Or was it a siren you heard? The implications are obvious and the necessary responses completely different.

  “The second thing you need to know,” says Corcoran, “is where are the safer and less safe places. And not just where you live, but where you live, work, and play.” In other words, plan an evacuation route to safe ground from any place where you spend a considerable amount of time.

  “Develop an eye for the landscape,” Corcoran suggests. “So, when the Big One occurs and we’re out driving around conducting our lives, we’ll have some sense of, ‘Wow, I’m in a bad spot. I need to get over there.’ Or, ‘Wow, I’m in a good spot—relative to tsunamis—I’m gonna stay put.’

  “The third thing,” Corcoran continues, “is how to reconnect with your loved ones. After the Cascadia Subduction Zone earthquake and tsunami, it’s going to be very difficult to get a hold of family members. There will be no phones. And you will not be driving anywhere.” He suggests that families pick a rendezvous point somewhere on safe ground and plan for all family members to meet there. That way everybody knows that everybody else will eventually make their way to the same place even if there’s no way to communicate.

  Corcoran asks people to imagine the nightmare of successfully escaping the shockwave and then deciding to go back into the disaster zone in search of a family member who has already escaped and is en route to a rendezvous p
oint or rescue center. A person could die for lack of planning. “Actually, the important thing is sitting around the kitchen table with your family and thinking through some scenarios. If this happens, what would you do? Well what if you’re at school? What if you’re at work?”

  What it comes down to is this: when the Big One hits, you’re on your own. This is all about self-reliance. And helping your neighbors.

  What if, as some emergency planners have suggested, people were able to escape the inundation zone by climbing a set of stairs instead of running halfway across town horizontally? The concept of “vertical evacuation” seemed to make instant good sense. To compare the official evacuation route with a hypothetical plan B, Patrick Corcoran agreed to run for his life again.

  Poised again at the base of the Lewis and Clark statue, this time he ran only three city blocks to the nearest easily accessible building that was more than three stories tall. The most recent computer model for Seaside has suggested the waves from Cascadia could be ten meters high, or a bit more than thirty feet, a monster by any measure. Just one block inland from the beach is a public parking building with four or five levels, just enough vertical amplitude to get us above a thirty-foot wave.

  Corcoran didn’t need to click the stopwatch this time because it was obvious he would make it to the parkade well before the imaginary tsunami hit the seawall. He took off at a brisk jog from the promenade to the first traffic light, where he hooked a quick right and headed for the stairwell door at the base of the building. The additional benefit of a parkade structure is the gently inclined ramps. People in wheelchairs or those who cannot thunder up the stairs as Corcoran did would still be able to gain some elevation without having to go all the way across town.

  Every beach town I’ve ever seen has always had a shortage of parking spots. What if city hall—with help from senior levels of government—were to solve their parking problem and save lives at the same time? All they’d need would be a building designed and engineered to withstand both the seismic shaking and the torrent of water.

  It just so happens that FEMA, the Federal Emergency Management Agency in the United States, the USGS, NOAA, and all five Pacific Coast states have already commissioned a study of that very idea. Not a parkade, necessarily, but earthquake- and tsunami-resistant vertical evacuation shelters. The engineering study was only one component of the National Tsunami Hazard Mitigation Program created by the U.S. Congress in October 1996—the product of lobbying efforts by people like Eddie Bernard and Lori Dengler in California in the wake of the Petrolia earthquake.

  From deep-ocean warning buoys and computer models to estimate and predict tsunami run-up and inundation zones town by town and beach by beach, the United States, at least, seems ready to take seriously the job of making coastal communities “tsunami ready.” Harry Yeh, a civil engineer at Oregon State University and one of the three principal investigators on the shelter study, believes most of the critical engineering problems could be solved and the proof was in Sumatra.

  In 2005, as engineers studied the tsunami aftermath in Indonesia and Thailand, everywhere they looked, “well-engineered, reinforced concrete structures were still standing,” said Yeh. He showed me a picture, drawing my attention to an apartment block or hotel right at the waterline in Banda Aceh. “Even though the structure was completely inundated to the roofline,” he said, “the structure itself is still standing. So our experience says that if you have a well-engineered concrete structure, I think those can be used for tsunami shelters.”

  Yeh also showed me other pictures of an odd-looking, cone-shaped building erected in a coastal town in Japan, where the concept of vertical evacuation has been studied, debated, and implemented already. In some places the top floors of apartment blocks, warehouses, and public buildings have been designated and prominently marked as tsunami shelters. Stairwells and doors to the rooftops are never locked. Local residents have been assigned specific numbered or marked spots for their families in case of an emergency. Regular drills are conducted in which able-bodied neighbors practice carrying senior citizens and disabled people to the top floors.

  In the small town of Taiki, the Nishiki Tower was custom built to survive the effects of the expected Tokai earthquake. It was also hydrodynamically designed to withstand the forces of fast-moving water. With rounded, conical walls and a spiral stairway to the top, it has shelter rooms and emergency supplies on the upper floors. The thing is—it looks odd—like a tall, white lighthouse in the middle of town, completely out of place. And that causes out-of-town visitors to stop and ask questions.

  “If I see such a tower,” Harry Yeh speculated, putting himself in a visitor’s shoes, “I’m gonna ask the people, ‘What is this?’ So everybody will know that’s a tsunami shelter.” He smiled. In essence, looking odd or out of place could help a tsunami shelter save lives. “I think this is a very important component of the design,” he said. In the meantime he and a study team continued to work on a new set of building code guidelines for vertical evacuation shelters.

  Among the engineering challenges, according to a report issued at the end of the first phase of the study, was that designing a building to withstand a seismic shock is in some ways the opposite of what you’d need to survive a tsunami. To ride out an earthquake, a building needs “flexibility, ductility and redundancy.” To outlast a tsunami it needs “considerable strength and rigidity, particularly at the lower levels.” But Harry Yeh insisted these requirements “need not be contradictory” and stressed that both had to be taken into account.

  The foundations of a tsunami shelter would have to withstand not just the violent shaking but the soil liquefaction that often accompanies a quake. They must be deep enough below unstable soil to be anchored on firm bedrock. The building itself would have to provide enough floor space for evacuees and be tall enough to stand above the largest expected wave. The walls would have to be strong enough to withstand the battering-ram effect of water-borne missiles (floating cars, logs, lumber, and other debris). It would have to be fire resistant since quakes and tsunamis always cause numerous fires to break out. The final design requirement would be resistance to scour. The foundations of a shelter would have to withstand the rapid rise and fall of fast-moving water that would “loosen the soil skeleton” around the building, possibly causing collapse.

  While the challenge sounds daunting, the report underlines the obvious concern that vertical evacuation may be “the only choice for human survival” in many coastal communities. Because of the engineering complexity shelter designs will probably have to be done on a case-by-case basis. Every beach and the bottom of every bay is a little bit different.

  CHAPTER 23

  Watching It Happen, Wishing It Wouldn’t

  Harry Yeh, Patrick Corcoran, and Chris Goldfinger met on the campus of Oregon State University in Corvallis for one of the most riveting demonstrations of the power of moving water I’d ever seen. Behind the blue-gray corrugated metal walls of a hangarlike building that looked big enough to hide a blimp, in a wave research basin half the size of a football field, researchers led by civil engineer Dan Cox had built a scale model of the town of Seaside, Oregon. The object of the exercise was to test the effects of a tsunami from Cascadia’s fault on a detailed physical replica of Seaside’s downtown core. Computer models had already predicted what would happen, but how would real water behave compared to a hypothetical digital clone?

  Graduate students and technicians from OSU had spent months building plywood surrogates for each of the main beachfront hotels, commercial buildings, parkades, and homes in the downtown area. They built an inclined platform and poured a concrete floor at exactly the same angle as the sea floor and beach. They constructed a breakwater exactly like the real one that stood beneath Seaside’s popular promenade. They marked out a duplicate street grid and used bolts and nail guns to anchor all the buildings into the concrete. From above it looked remarkably like the real thing, only fifty times smaller.

&nb
sp; Dan Cox and his team then programmed a sophisticated set of computer-controlled mechanical paddles at the far end of the basin. The system was capable of generating a scaled-down version of Cascadia’s wave: one-fiftieth the size of the real one oceanographers and marine geologists expect to see crossing Seaside beach some day in the unpredictable future.

  A special-effects camera team filmed the experiment (for the ShockWave documentary) so others could observe the results. To visually slow down a lump of water moving fifty times faster in the tank than the real wave would sweep across the beach at Seaside, we used a special high-speed camera that could shoot up to 1,500 frames per second and still deliver a high-definition color picture. We used a snorkel attachment to create a pedestrian’s eye view of the tsunami as it moved up Broadway. We were able to play back the wave experiments on a large-screen, flat-panel TV display. On a work table beside the giant monitor, a computer terminal had been set up by Patrick Lynett, a scientist from Texas A&M University who had been working for months on a parallel experiment to refine a numerical model designed to match the bathymetry and layout of Dan Cox’s model of Seaside. They would run their waves simultaneously and compare results.

  For Lynett and the many others involved in the computer modeling of tsunamis, the running of a wet physical replica of Cascadia’s wave in a test basin like this at OSU would provide a crucial benchmark—a reality check for the mathematics. If the two models showed pretty much the same results, then an extra measure of confidence would be gained for the computer simulations. A large physical replication in concrete and plywood for each of the dozens of communities threatened by Cascadia would never be affordable, either in dollars and cents or in the amount of time it would take. But if a computer model could reliably tell you the same thing, physical models wouldn’t be necessary.