Cascadia's Fault - Jerry Thompson [84]
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