Updated TSUNAMI model for M9 Cascadia earthquake

tsunami inundation animation

Tsunami animation at hour +3; the first pulse has entered Bellingham Bay (upper right) to a height of around 3 m above sea level. Click to enlarge.

On January 5th the NOAA Center for Tsunami Research released a new model for tsunami inundation in the Straits of Juan de Fuca and inland waters of Puget Sound and the Salish Sea from a great Cascadia Subduction Zone earthquake.

An animation is published by the Pacific Northwest Seismic Center and can be watched here https://www.youtube.com/watch?v=YhjsAjZQZeg&app=desktop The animation gives elapsed time on the right and inundation heights in meters. Of particular interest is the effect in the San Juan Islands and Bellingham Bay. Contrary to popular belief, the San Juan Islands DO NOT block the tsunami, but rather concentrate it in the narrow passages. Watch the animation several times and keep an eye on Bellingham Bay, just west of the ‘elevation’ legend, in the northeast corner of the map.

You’ll see that three tsunami pulses enter the Straits over a period of 6 hours after the earthquake. The first pulse enters Bellingham Bay about 3 hours after the earthquake, and reaches a height of 3-5 meters (10-16.5 feet) and remains ponded in the enclosed bay for around 1 hour. The water then recedes to around -1 to -3 m (-3.3 to -10 feet) by the fifth hour, to be followed by a second tsunami pulse at 6 hours, about the same depth as the first. This also drains; the animation ends at the hour 8, as a third pulse is reaching the west coast of Whidbey Island and the San Juans. This one does not appear to be as high as the first two.

The model extends as far south as Olympia. The greatest height in southern Puget Sound occur in narrow constrictions- near Bremerton and Alki Point in Seattle.

The model is worth watching several times- you can stop and start, as well as backtrack with your cursor.

For more info on the model, read the research paper by Venturato et al., 2007:  http://www.pmel.noaa.gov/pubs/PDF/vent2949/vent2949.pdf The study focuses on Pacific coastal communities of Washington. The model has been newly extened to inland waters.



2 Responses

  1. So, the west side of Whidbey is a nice place to visit, but……..

  2. Great info, thanks Dave.
    The time delay projections are quite interesting…good to know we have a bit of time to dig out from under any debris from the quake before the waves hit.

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