Is a tsunami a possibility here in Edmonds?

By Bob McChesney, Executive Director, the Port of Edmonds | Mar 17, 2011

Could a tsunami occur here in Edmonds? Absolutely, and here at the Port of Edmonds we have long recognized that the single greatest way to minimize the impact is preparedness.

For a large earthquake beneath Puget Sound to cause a tsunami is not only possible, it has occurred. The famous Seattle fault runs east-west directly across Puget Sound. A magnitude 8 quake about 1,000 years ago lifted areas of the shorefront of eastern Bainbridge Island twenty feet. It is thought to be the cause of a tsunami recorded in beach sands about the same time.

Here at the Port our staff is continually being trained to deal with major emergencies of all kinds and in the last decade we have been a participant in a federal Sea Grant program to develop a prototype for tsunami warning and preparation.

Often erroneously called a tidal wave, a tsunami is a catastrophic wave that is usually caused by a 6.5 or greater submarine earthquake occurring less than 30 miles beneath the seafloor.

As the events of last week have reminded us, they are serious business. Worldwide, there have been 26 tsunamis that caused 200 or more deaths in the last century alone. The 2004 Indian Ocean earthquake and tsunami killed over 200,000 people; in 1992 and 1993 over 2,000 people were killed by tsunamis in Nicaragua, Indonesia and Japan. In 1998 a tsunami killed 2,200 in Papua, New Guinea.

Nor are they limited to other countries. In 1964, Crescent City, California was struck by five tsunami waves generated from the earthquake in Alaska. Twenty-nine blocks of the town were demolished and eleven people died.

According to the University of Washington, the Northwest is capable of producing huge quakes and tsunamis, mainly as a result of an offshore geological feature called the Cascadia subduction zone. Major subduction quakes appear to happen every 300 to 700 years. The last one occurred in 1700.

When our state-of-the-art Edmonds marina was rebuilt in 1997, it was designed with major earthquakes and tsunamis in mind. Because of the truss-like roof design of our docks, the floating parts of the Port of Edmonds would undoubtedly come through a major tsunami in better shape than other West Coast marinas hit with comparable force. Earthquake and tsunami resistance are essential design criteria for all structures being considered at the Port and Harbor Square.

On a personal note, I would like to thank one of my predecessors, Bill Toskey, for much of the information in this piece. His well-versed expertise on tsunamis, earthquakes and other natural disasters contributed not only to this column, but to the material strength and preparedness of today’s Port of Edmonds.

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