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  1. It’s helpful to think of a seismic sea wave as a flash flood. They are structured like regular waves, except that they have a length — a wavelength, the distance from crest to crest or trough to trough — of perhaps 100 miles or more (a low frequency, meaning not very frequent). When a regular wave hits the shore, it goes whoosh, the water comes up and goes back out because the length is relatively short. The long wavelength of the tsunami makes the impact of the wave appear to be a flood. On Hilo, the tsunami waves from Chile had a frequency of 20 minutes (times 500 miles per hour = a wavelength of about 165 miles) and a height (amplitude) of about 2.2 feet or so. There are spots on the south coast of Alaska that show evidence of tsunamis hitting shore and inundating mountainsides up to 500 feet above the ocean. Hawaii got lucky this time.

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