Researchers simulate tsunami in Seaside

Story Posted: Fri, Sep 14, 2007

By Winston Ross
The Register-Guard

Published: Friday, September 14, 2007

CORVALLIS - The kind of tsunami that comes only every 300 to 500 years struck Seaside twice on Thursday, a feat possible only because the waves were generated by a machine and the town was a collection of miniature wooden buildings and concrete slabs at Oregon State University's O.H. Hinsdale Wave Research Laboratory.

"This is sort of a 'sim'-tsunami," explained Harry Yeh, an ocean engineer professor at the college.

The exercise was meant to demonstrate a couple of things about what would be the worst natural disaster in history to hit the Oregon Coast. One, there's precious little time to get out of the way of a 35-foot wave in a place that's very close to the fault line that would cause the tsunami. And two, the best escape may be skyward.

Because Seaside's downtown is so flat, the search for higher ground will be futile for those who are not able-bodied - and aware that they need to run for the distant hills the moment they feel the ground shake.

A 500-year tsunami, which would follow an earthquake with an expected 9.0 magnitude, doesn't give people in a place such as Seaside many options. Plus, on a summer day the town's 5,000 residents are often outnumbered by tourists, who may know nothing about what to do when the water starts being sucked out to sea.

That's why professors hope to accomplish two objectives with the model of Seaside they've built at the wave research lab. They want to find out which buildings would be buried in water, so that they can compare the results with computer-generated guesses about where the waves will go. And they want to figure out whether there's a better alternative for some folks than to race away from the onslaught along roadways that will likely be buckled in the quake.

To answer these questions, scientists and engineers will place optical sensors in the miniature village, which is fifty times smaller than the actual town. The sensors will collect data as a hydraulic ram simulates a tsunami by pushing a wall of water across a basin and towards the waiting "buildings." The sensors will gather information about how high the waves are, how fast they travel and how deep they will be, once the town is inundated.

Since the models are accurate representations of what's in Seaside, based on images from maps at Google, that will give researchers an idea about whether it might be safer for some to climb to the top of existing buildings, rather than run east to safety.

The research could also determine whether it would be a good idea to build vertical shelters like the ones in Japan, so that residents can flee upward. Engineers will install high-speed still and videocameras to record the waves' arrival, another way to determine how tall a building should be to avoid the wrath of an incoming tsunami and how accurate the researchers' guesses have been thus far.

During Thursday's exercise, researchers created what would be a 35-foot wave in real life. It crashed violently onto the faux shoreline, surging above the promenade that fronts Seaside and the row of hotels behind it. Then the wave continued to the edge of the "inundation zone," the area where the water is expected to travel, and flooded the remainder of the town.

"How good are our computer simulations?" Cox said. "Are vertical evacuations an alternative for Seaside?"

What they won't know is how all that changes with the earthquake, one that will be so massive it will topple many buildings and bridges and buckle area roadways.

"You isolate what you can do and say something conclusive about it," Cox said.

Winston Ross can be reached at (541) 902-9030 or rgcoast@oregonfast.net.