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New tsunami peril maps display how a Cascadia megaquake could influence Puget Sound

June 22, 2021By catalen McKeegan, Science interactions Fellow 

It’s no a matter of if, yet when. New tsunami risk maps released by the geology Survey and also the State room of organic Resources (DNR) display that a huge earthquake on the Cascadia subduction region (CSZ) turn off the coast could reason a tsunami that will not just reach the Puget Sound and Hood Canal, however will leave part low-lying locations under 14 feet the water. 

The tsunami models and high resolution basic maps offered to do these new tsunami risk maps predict tsunami inundation along Puget Sound shorelines native a size 9 earthquake on the CSZ. A decade ago, many thought that Puget Sound would be for sure from Cascadia tsunamis. However, these brand-new hazard maps show that no only can Cascadia tsunamis make it right into Puget Sound, however some areas will have actually onshore inundation. This maps, which identify “hot spots” for such tsunami hazards, have the right to be supplied as a tool to educate emergency planning and also evacuation courses in the occasion of a Cascadia earthquake. 

“People didn’t really think that was something we essential to problem about,” Carrie Garrison-Laney, Sea give tsunami perils specialist, explains. Garrison-Laney is a contributor come the tsunami risks report and also shared geological evidence of past tsunamis close to Belfair in Hood Canal. “These maps are causing excitement since they cover locations that have not been studied before.” previous tsunami danger maps in Puget Sound were limited and modeled the impacts of tsunamis caused by local earthquakes from faults much closer come home, favor the Seattle fault.

Producing this maps involved many years of collaboration between several various agencies, including the national Oceanic and Atmospheric management Center for Tsunami study at the Pacific Marine ecological Laboratory, a team of modelers from the university of, and also the geology Survey, part of the room of herbal Resources. Modeling capability have substantially improved in recent years, many thanks to far better computing power and also the greater resolution maps supplied in modeling, otherwise known as Digital elevation Models (DEMs). “Tsunami models usage offshore bathymetry and onshore topography to design what the wave does together it moves from the marine atmosphere onto land,” Garrison-Laney explains. “The much better the DEM, the much more confident you have the right to be in the model results ” 

The brand-new models and maps present how, in some hot spots, a tsunami could cause inundation and dangerous currents in inland areas. The port of Tacoma might see depths of 3.5 feet. Seattle’s harbor Island could be inundated approximately 4 feet. One major hotspot is Belfair, located at the guideline of the Hood Canal, which might see as much as 14 feet the water. However, the not just the inundation that we require to problem about. A Cascadia event could cause dangerous currents in Puget Sound, reaching accelerates to 9 knots in the Agate Passage north of Bainbridge Island and 6 knots turn off of discovery Park in Seattle.


These maps are based on only one Cascadia scenario. Over there are other tsunami scenarios that are not accounted for in these maps, such together tsunamis caused by landslides or local earthquakes top top the Seattle fault. However, the models administer a much better indication the which locations in Puget Sound are likely to have actually tsunami flooding and also can be supplied as a tool to inform decisions approximately emergency preparedness. “I don’t live in the tsunami inundation zone, but when i go stay somewhere the end on the coast, it’s always on mine mind,” admits Garrison-Laney. “It’s a genuine hazard.

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The big tsunami events in 2004 in the Indian Ocean and in 2011 in Japan yes, really woke human being up. It was a shocking reminder the what we might confront here.”