Chile quake 2010: Tsunami warning system worked as intended
The Pacific basin's warning network detected the Chile quake's tsunami accurately, and computer models are improving, tsunami experts say.
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But the true forecasting challenge comes as the tsunami interacts with the near-shore bottom, Dr. Murty explains.Skip to next paragraph
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Valpariso, Chile, roughly 200 miles north of the quake's epicenter, experienced a tsunami topping 8 feet, while Robinson Crusoe Island, 400 miles offshore, was struck by a wave that reportedly killed four people. Eleven others remain missing.
By the time tsunamis began arriving in Hawaii, Hilo experienced tsunamis less that three feet tall.
Size isn't everything
Less than three feet may be puny by James Michener standards. But Eddie Bernard, a tsunami specialist and director of the National Oceanic and Atmospheric Administration's Pacific Marine Environment Laboratory in Seattle, notes that even small tsunamis can inflict damage, particularly in harbors. The repeated surges can smash boats against each other or against docks. And once a tsunami enters a harbor, it can in effect reverberate within the harbor for hours, much as sound waves from a bell reverberate.
Moreover, even small tsunamis can temporarily alter currents in dangerous ways, Dr. Bernard says. That was the sort of response recorded in L.A. Harbor.
"We were lucky the tsunamis came at low tide; the currents were not as strong as they could have been" at the harbor, he says.
But he adds that more needs to be done to improve site-specific forecasts.
One step forward came following the Sumatran earthquake in 2004. With input from countries in the region, NOAA put together a web-based model that allows countries to make site-specific projections. The model, which can be downloaded and run on a typical laptop if the number of sites is small, allows local managers to project potential wave heights and in-harbor reverberations as a tsunami comes ashore.
At this stage, for the US, the model focuses on harbors, Bernard says. The reasons: the high value of ships, cargo, and other assets stored there; and that's where the best tide gauges are, so model projections can be tested against real-world measurements and the models improved.
Over time, as confidence in the models increases, he says he expects that national, state, and local governments in the Pacific region and elsewhere – particularly among developing countries – will be able to extend the use of the model to larger lengths of coastline to include resort areas and smaller coastal cities.