Cascadia's Fault (25 page)

The Petrolia story rang bells in the state capital as well, according to Dengler. “It brought the emergency management community into the picture. Prior to our event, I would say most emergency managers in the state of California weren't really convinced that Cascadia was a problem. They had a really rapid conversion,” she declared. “And so we saw an incredible surge in momentum with NOAA and the emergency management community, which really culminated in the planning scenario for an 8.4 earthquake on the Cascadia Subduction Zone.”

Dengler paused, looked up, anticipated my next question, then answered it all in the same breath. “Some people say, ‘Well, why an 8.4? Why does it
stop
at the California border?'Well, this was funded by the state of California. And so, it's a great document, but it certainly has its limitations.” I took this to mean that the mandate for emergency planning by the governor's Office of Emergency Services ends at the California state line. The larger scenario for a magnitude 9 catastrophe along the entire Cascadia margin would have to wait until other state, federal, and provincial governments were sufficiently motivated to get involved. For these other jurisdictions to the north, apparently the tipping point had not been reached yet. The good news was that awareness
of Cascadia, along with a new sense of urgency, had now spilled across the boundaries from geology to the liquid sciences as well.

 

Before Sumatra, very few people had seen a tsunami in action. Until those chilling home videos from Thailand and other fatally ruined vacation resorts were broadcast round the world, hardly anybody in the general public knew what a tsunami could do. Even the experts, oceanographers like Eddie Bernard at PMEL and top-ranked wave modelers like Vasily Titov, had only a theoretical appreciation of the beast they were dealing with. They understood the hydrodynamics, they could do the math and had seen photographs of damage done by waves in the distant past, but until Sumatra neither had seen the real thing in real time.

Before Sumatra, the most recent and memorable tsunami had been the one triggered by the 1964 Alaska earthquake. “I was born in 1962,” Titov volunteered, “so I was two years old. I didn't know anything about the tsunami personally. I knew everything from the [scientific] publications and from my studies.” Only a few people in affected communities worldwide had ever seen a killer wave and the tsunami scientist who had experienced one was an even greater rarity. Titov set out to solve this problem by capturing a wave in a computer.

He wanted to master the mathematics—and the art—of digital water. If he could learn enough about fluid dynamics to reproduce the behavior of a wave with a numerical model in a computer, he and his colleagues might be able to improve the world's tsunami warning systems and save lives. He recalls how hard it was before Sumatra to get people interested in or even concerned about this rare monster from the deep.

“There was very little awareness in the larger society about the danger of tsunamis,” Titov said. “It was difficult to convey this message to society because the first question people would ask is, ‘When was the last big tsunami?' And you say, ‘1964.' It just doesn't sound that convincing.” To many the threat seemed as farfetched as getting hit by
an asteroid. The work remained an arcane specialty practiced by an elite group of gifted mathematicians who could have held their conventions in a phone booth.

The study of wave mechanics had begun with work on hurricanes and typhoons about twenty-five years earlier. Hurricane science had decent funding because people saw the destructive power of these storms and their waves several times every year. Most of the world's impression of tsunamis was based on scraps of grainy film footage shot decades ago in Hawaii or Japan or on badly faked waves in B-grade Hollywood disaster flicks.

The émigré math whiz Vasily Titov, however, was destined to change all that and NOAA's Eddie Bernard helped make it happen. Titov was one of the new wave of modelers Bernard assigned to the Cascadia problem not long after the Petrolia earthquake. “His models are—the way they convey so much information in such a short amount of time—can only be called art,” enthused Bernard, “because in science that's not easy to do.”

They first met in 1989 at an international tsunami conference held at the Novosibirsk Institute of Electrical Engineering in Russia—at the geometric center of Eurasia, the world's largest continent. “I remember the banner,” said Bernard, picturing the slogan that adorned the meeting hall: “‘We are the furthest from any coast in the world, so this is the safest place from tsunamis in the world.' And I think that's true.” He laughed, enjoying the irony.

Titov wanted the chance to work with state-of-the-art equipment to develop software that could anticipate the behavior of big waves. “Realizing how dangerous this phenomenon is, we definitely were working on the science of describing the tsunami with the ultimate goal of actually forecasting it,” Titov told me. Folding geology, oceanography, and hydrodynamics together in a package that could mine data from several sources at once and then create animated waves that accurately mimic nature in real time was a tall order on a shoestring budget.

So he eventually moved to Seattle, where he joined Eddie Bernard's research team at NOAA's Pacific Marine Environmental Laboratory. Money and technology aside, the odds of getting something like that to work seemed as steep and improbable as forecasting earthquakes or asteroids. Even the best supercomputers back then were struggling to imitate the flow of water. Adding the complexities of gravity and friction across rough surfaces along the bottom, undersea mountain ranges that could steer a moving wave in a new direction, and the infinitely convoluted bathymetry of every harbor and beach—all of which would affect the movement of a tsunami—was a daunting prospect even for someone who loved math. Titov packed his kit and moved from the safest, most tsunami-free zone in the world to one of the most dangerous.

 

On July 12, 1993, little more than a year after Cascadia's fault started unzipping in Petrolia, California, another powerful Ring of Fire earthquake tore the ocean floor west of Hokkaido in the Sea of Japan, hoisting a mountain of seawater that quickly broke under the force of gravity into a series of tsunamis. On nearby Okushiri Island seismic damage was only one of several disasters. Toppled fuel tanks and broken gas pipes fed fires that spread rapidly through the rubble. Cape Aonae, a peninsula on the south end of the island, was completely overtopped by thirty-foot (10 m) waves. The highest tsunami to hit Okushiri was almost thirty meters—a wall of water nearly a hundred feet high.

The scariest part was that all of this happened in the middle of the night, so people living there never saw the tsunamis coming—yet they clearly knew what to expect. The Japanese had learned enough from painful experience with earthquakes and tsunamis that most of the island's residents instinctively moved to higher ground as soon as the earth started to rumble. Almost two hundred died and many thousands were injured. Homes, businesses, and the main harbor were badly damaged. The toll would have been far worse if more people had lingered in their wrecked villages only to be drowned by the train of towering
waves that hissed and roared from the darkness and slammed ashore a short time after the jolt.

There was little that Vasily Titov could do personally for the people of Okushiri Island. By the time he moved to PMEL in Seattle, however, his tsunami model was advanced enough to be ready for a real-world test that might help others in the future. He and his research partners gathered a wealth of new details from the Japanese about where the water went and how high it reached along the beaches. In the tragedy of Okushiri Island there might be just enough new “data points” to fine-tune his and several other models that were being developed so that lives could be saved the next time.

“We cannot say when the next big earthquake is going to happen,” said Titov. “However, from the moment a tsunami is generated, if you know some data about the tsunami, our model can actually tell you pretty well what happens next. How high the tsunami wave is going to be at the coastline, how big the impact is going to be at a particular location. The only thing we have to know for that is the measurement of the wave.” Not surprisingly, Japanese scientists had made very precise observations of what happened on Okushiri and along the Hokkaido coast.

One of the many tricks to making a computer simulate a tsunami was learning how to create numerical codes that could reproduce the nonlinear movement of water as a tsunami got bigger and bigger. Before the 1993 wave, Titov and others had created several digital simulations that accurately mimicked the behavior of water in laboratory tests. Titov's software even performed well in terms of predicting the outcome of a real tsunami generated in the Aleutian Islands.

“It was not a forecast in the operational sense of the word,” Titov conceded, “but I had all the components in my computer. And when the tsunami came, the comparison was so good,” he paused, searching for the words, “I could not believe my eyes. In a nutshell it performed much better than expected.” The Aleutian tsunami that served as his
earliest test case was another of those relatively small waves that caused little damage. He knew that bigger waves were
not
just more of the same. At a certain point they morphed into something else entirely. Two plus two could add up to five or even ten in the nonlinear world of killer waves.

“Tsunamis are such beasts that they change their attitude, if you will, when they grow bigger,” Titov explained. “It's sort of a trivial thing to say, but in terms of a mathematical model, it means that it goes from the linear stage to be a nonlinear phenomenon. And nonlinear is much more difficult to predict, much more difficult to model.”

The NOAA team needed data from a larger wave to plug in to the computer if they were to see how well the model mimicked what happened when nature went on a rampage. “What was missing was the big event,” said Titov, meaning a wave that could “test the system from the beginning to the end.” That event—the wave that became the benchmark for his model—was the one that hit Okushiri Island in July 1993. He and colleague Chris Moore took the camera crew and me to an editing room where they showed us the results on a large, high-definition flat-panel screen.

The images mesmerized everyone in the room. There in full 3D relief stood Okushiri Island as the leading wave approached the beach. Instead of black night we could see it all in perfect daylight detail, a view from space that could zoom right down to sea level and hover at any angle to see what the wave would do from every conceivable perspective. Titov and Moore had taken data points from the Japanese scientists, entered those numbers into the computer and rolled the timeline backward to the beginning.

Knowing how the wave ended—how high it pegged the needles on tide gauges, how far up the various beaches it ran—they reverse-engineered the event all the way back to flat water the moment before the Hokkaido quake and could play it again and again by clicking a mouse. This was more than just high-quality 3D animation—they had
converted raw data into computer code to recreate the wave, then converted it again to graphical animation files that let them “fly” through the air above Okushiri and look at every hair on this monster's head.

When they hit playback, they ran the event in slow motion to examine exactly how the waves changed shape, size, and direction as they rolled uphill from deep water, scraping across the rough terrain of the foreshore, the fronts of the waves slowing down because of friction and a heavy load of silt and the trailing edges still moving fast, rising high and crashing hard at last against dry land. It was amazing to see, especially when I reminded myself that this was based on real data from the real wave, not the fantasy of some Hollywood special-effects studio.

“What I like about it,” said Chris Moore, his hand on the mouse, “is the aerial photograph pasted over so that you can actually see exactly where the town is situated with respect to the wave.” It looked like Google Earth come to life in 3D. “This is an airstrip.” Moore nodded at the screen. “Each of these little dots is a rooftop—in reds, whites, and blues. So you can sort of see approximately how large the wave is.”

Moore pointed to the small peninsula that was about to be overtopped by the tsunami. In the animation a train of three waves approached the beach. “Here it's shallow,” he said, hovering the cursor near the southernmost tip of land. “It's deeper water off of here.” He moved the cursor farther off the beach. “And this wave front, as it animates through, tends to bend around the headland because the wave is slower in shallower water and faster in deeper water. So it bends right around there.”

The computer made it perfectly obvious why the waves would slow and turn as they did. “And then this group of waves here . . .” Moore zoomed closer to a second point of land, the graphics revealing a steep cliff overlooking a small bay. “It also shows reflection off of that headland.” The incoming waves bounced off the wall of rocks and ricocheted back across the bay to hit what had been a sheltered cove on the lee side of the incoming tsunami's path.

Suddenly Titov tapped the space bar to pause the wave. “See this
kind of fissure when the wave withdrew from the coast and formed a hydraulic shock?” He pointed to a frozen wall of water standing just beyond a beach that had been completely drained of its surf right down to bare sand. “That's the first time—this animation—is the first time I saw anything like that. And if there was no animation, we probably wouldn't have picked it up.”

“Yeah,” Moore enthused, “let's just single-step through it and see how it goes.” He rewound the wave ever so slightly and played it back frame by frame. “So right about here is where it's forming,” he mumbled as the leading wave fell back down the beach, taking all the water with it. “So this water is receding just as the next wave is coming in. It's almost forming a standing wave or hydraulic shock.”