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Session 33 - Comets & Asteroids.
Oral session, Wednesday, January 07

[33.07] Down-to-Earth Astronomy: Tsunami from Asteroid-Comet Impacts

J. G. Hills, C. L. Mader, M. P. Goda, M. S. Warren (LANL)

We have begun a systematic study of tsunami produced by the impacts of asteroids and comets on Earth. As the first phase of this work, we have looked at tsunami produced by the impacts of moderately large asteroids, 5-6 km in diameter, in the middle of the large ocean basins. This work is to identify coastal areas that are most susceptible to impact tsunami. We find that areas with gradual continental shelves such as the British Isles in Europe and Florida in the United States are less susceptible to impact tsunami while regions with little continental shelf are the more exposed. Gradual continental shelves tend to reflect the tsunami back into the ocean. An asteroid 5-6 kilometers in diameter hitting in mid Atlantic would produce tsunami that would travel all the way to the Appalachian Mountains in the upper two-thirds of the United States; e.g., Washington, D.C. would be washed out. In Florida, the damage would be much less except in the area from West Palm Beach through Ft. Lauderdale to Palm Beach where a deepwater shipping channel would funnel the tsunami energy to shore. In Europe, the most susceptible area is the Spain-Portugal peninsula, which has very little continental shelf. In retrospect, this result is not surprising as this peninsula has been subject to earthquake tsunami during the last few hundred years. An asteroid 5-6 kilometers in diameter impacting between Hawaii and the West Coast would wash out the coastal cities. The area between Los Angelos and San Diego is particularly vulnerable. This same impact would produce tsunami that would cover most of the land area of Oahu, the most populous Hawaiian island.

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