Cascadia's Fault (42 page)

“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 point 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.

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.

In principle, if Lynett's model worked well for Seaside, then it could be reprogrammed and modified with new bathymetric and street grid details for the next town on the coast, and a more realistic appraisal of the inundation zone and specific levels of risk could be had much sooner and at lower cost. At least that was the theory and the reason that people like Dan Cox and Patrick Lynett were eager to see what happened next.

Chris Goldfinger, back from his research cruise to Sumatra, offered a sobering caution. The numerical simulation of anything as sloppy as moving water is extremely difficult to do. It was hard enough to work on a broad, oceanwide scale as Vasily Titov had done, but even more challenging when you tried to zoom in to detailed street grids and individual buildings in a single town. The tighter the grid, the more exacting the model, the greater the chances for error.

“The best computer models now are working hard at quantifying the flow [of water] around
one or two
objects,” Goldfinger explained, “a cylinder, a bridge piling, something like that—a relatively simple case—just because the computational time is enormous.” When the myriad three-dimensional obstacles in a real harbor and town are assigned numerical values—the friction coefficient for water moving over the sandy ocean bottom, a different level of friction and drag once the swell crests, crashes over the seawall, and begins moving over dry ground cluttered with buildings, cars, trucks, trees, and lumpy terrain—it gets a lot more difficult.

After a quick check by portable radio with the crew standing by in the control room to confirm that the computer and the paddles were ready, Cox turned to his visitors. “So what you're going to see next,” he explained, “is the rough equivalent of the five-hundred-year-event.” Meaning the full-margin rupture of Cascadia's fault that takes place on average every five hundred years. “So this is a twenty-centimeter lab scale or [the equivalent of] a ten-meter full-scale tsunami that is coming into Seaside.” Quickly doing the conversion in my head, I tried
to picture a surge of water more than thirty feet above the high tide, thundering toward the beach.