Hawaii's tsunami warning: How the US is better prepared.
How has the US become better prepared to forecast tsunamis?
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In addition, NOAA received funding to keep its two tsunami-warning centers, one based in Honolulu, the other in Palmer, Alaska, operating full time, notes Jenifer Rhoades, the tsunami program manager for the National Weather Service.Skip to next paragraph
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The additional data these buoys provide, combined with advanced models of the sea floor along coasts and the behavior of tsunamis as they radiate from their source, allow forecasters to constantly refine their projections of likely wave height at landfall.
The buoys, which are set out on the sea floor and awakened by seismic waves from a quake, use sensitive pressure detectors to spot a passing tsunami. Saturday’s quake was so strong, it activated buoys in the Atlantic and Caribbean, although no tsunamis are expected there.
Overall, Washington invested some $42 million to beef up seismic and tsunami detection and warning efforts.
What's the difference?
Tsunamis differ from ordinary waves in significant ways.
The swells that roll along the open ocean to become a surfer’s playground originate at the surface as wind blows across it. Tsunamis, triggered by a sudden change in sea-floor height from an undersea quake, or from an undersea landslide involve the movement of an entire vertical extent of ocean.
As they reach shallow water offshore, they slow down and build in height. At sea, a tsunami’s height can be measured in inches and so are hard to detect at the surface. When they reach shore, however, they can mount to heights of several feet above normal surf levels.
Tsunami events typically involve several waves arriving over several hours. And the first wave isn’t necessarily the tallest, Ms. Rhoades explains.
Where a tsunami meets a bay or inlet, tsunami height is further magnified. In Alaska’s Cook Inlet, tsunami heights from the ‘64 quake topped 100 feet at some locations.
Yet it doesn’t take an overwhelming wall of water to inflict serious damage, Rhoades cautions. She points out that in flash floods, two inches of water can knock a person over.
“With a tsunami, even a foot of water moving at 35 miles an hour endangers life and property,” she warns.