Cascadia's Fault - Jerry Thompson [139]
Cox gave the order and moments later the long row of paddles at the far end of the tank thrust forward at the calculated angle and speed. A dark swell began moving, quietly hissing toward Seaside. The wave crashed against the breakwater and shot a slice of foamy spume straight up. In the next heartbeat the on-rushing tide poured across the promenade and churned up Broadway, sweeping up toy school buses, cars, and trucks in a frothy vortex that quickly swamped the entire model.
As a matter of interest I noticed that one prominent multistory hotel right on the waterfront had been completely overtopped by the wave. The upper deck of the parkade building directly behind the beachfront condominium complex had remained dry. Patrick Corcoran, standing elbow to elbow with the other observers on the pool deck, noticed it too. Anyone who could get to the top of that building would probably have survived, but anyone stranded at street level or anyone trying to escape in a car probably wouldn’t have had a chance.
When the sloshing finally stopped nobody said a word. Like Corcoran, many of those in the crowd knew the streets of Seaside well. It seemed as though everyone in the room was momentarily stunned, trying to absorb the news that most of the downtown area would be inundated by the pulses of seawater from Cascadia’s fault.
Patrick Lynett, meantime, had called up a file from his computer model and was explaining how he’d created a numerical duplicate of the objects in the basin. The first frame of his simulation of Cascadia’s wave looked like an animated cartoon of the physical model, a 3D aerial view of the miniature plywood buildings nailed to the concrete floor in front of us. His intention had been to make the layout of the numerical model resemble the built world of the research tank as closely as possible so that when he hit the run button, his computer-generated wave would face exactly the same obstacles. With any luck the digital tsunami would match the behavior of the real wave we had just witnessed.
As I watched the simulation play on the monitor, it looked pretty convincing to me. After pounding across the seawall, a dozen or more jets of dark-blue liquid surged past the first rank of buildings, pushing straight up Broadway and all the eastbound streets simultaneously, turning corners and twisting together like braided hair as they seemed to amplify themselves in thicker, darker currents along some of the narrow side streets.
“What we’re looking at here is momentum flux,” said Lynett, “which is a very good measure for the potential force of fluid for the tsunami as it comes in and inundates Seaside ...”
It wasn’t clear to me that anyone really heard what he’d said. They couldn’t take their eyes off the screen. This time we could see more clearly what the wave was doing because the computer had slowed it down to something resembling real time. With a click of the mouse, Lynett slowed it down even more and then stopped the action completely.
“If you look at this little building right here,” he said, hitting pause and pointing to what looked like a small house on a side street several blocks away from the beach, “what actually happens is—you get a wake off of this building.” He clicked play again and advanced the animation a few more frames. A thick wedge of the inky blue water pouring east on one street ricocheted off a larger commercial building across the street from the house. “It bounces off the side of this building—and additionally you get a large wake off of this building.” Now we could see the almost synchronous arrival of another tongue of water on the next parallel street. “And those two line up and just pound this tiny little building,” said Lynett.
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