Lessons from Indian Ocean tsunami lead to prevention measures locally

Contractors demolish a portion of the Ocasta Elementary School as they prepare to build a new school with the nation's first tsunami evacuation refuge. Photo courtesy Ocasta School District
Contractors demolish a portion of the Ocasta Elementary School as they prepare to build a new school with the nation’s first tsunami evacuation refuge. Photo courtesy Ocasta School District

Ten years ago today, a Magnitude 9.2 earthquake struck off the west coast of Sumatra, producing the single-most devastating tsunami in recorded history. The tsunami that swept across the Indian Ocean killed more than 230,000 people and left more than 1.7 million homeless.

The megathrust earthquake initiated from the Sunda trench subduction zone off the west coast of Sumatra.

This devastation is a strong reminder that Washington state is also vulnerable to this type of event. Closer to home, other reminders are tsunami deposits, drowned shorelines, and buried trees from the 1700 A.D. Magnitude 8.8–9.2 megathrust earthquake along the Cascadia Subduction Zone. These clues have been located in numerous places along the Washington, Oregon, California, and Vancouver Island coasts.

DNR’s Geology and Earth Resources Division, the state’s official geologic survey, is helping Washington communities identify how they are vulnerable to similar tsunami events and how they can craft innovative strategies for dealing with those threats.

Westport lies just off the Cascadia Subduction Zone, a 600-mile-long fault that runs from northern California to Vancouver Island, leaving it vulnerable to earthquakes and tsunamis.

Just 25 feet above sea level, the community is preparing by building a new $15 million elementary school that includes a tsunami refuge atop the gymnasium, the first such refuge in the United States.

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When built, the tsunami refuge will be capable of holding more than 1,000 people atop the 30-foot building designed to withstand both a megathrust Cascadia earthquake and the pounding of tsunami waves. It was designed by Degenkolb Engineers and TCF Architecture, through the efforts of Project Safe Haven, which was launched by the Washington State Emergency Management Division in 2011. Construction is expected to be completed by this time next year.

Thanks to continuing efforts, a tsunami berm is also proposed adjacent to the Long Beach Elementary School. The landscaped berm would replace an existing bleacher there and would hold about 800 people atop it during an emergency, while serving as an attractive amenity every day.

The 2004 Indian Ocean earthquake resulted in the Tsunami Warning and Education Act of 2006, wherein NOAA formalized and expanded the National Tsunami Hazard Mitigation Program, a partnership with Pacific states to protect the West Coast from tsunamis.

Hazards geologists with the Department of Natural Resources Division of Geology and Earth Resources, the National Center for Tsunami Research at NOAA’s Pacific Marine Environmental Laboratory, and scientists with the University of Washington model tsunami inundation in population centers both along the Washington coast and within the Puget Sound.

To do this complex math, the geologists use software (Clawpack), developed by the Applied Mathematics Department of UW or the MOST model, developed by NOAA.

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A recently published inundation map for the city of Everett models how a tsunami would likely impact the Everett area.

The Geology Division is now focusing similar efforts on the San Juan Islands

DNR has charted evacuation routes for those in communities that might be impacted by tsunamis on our interactive geologic map. The Division also documents tsunami-related news in our bi-monthly newsletter, TsuInfo.

For more on tsunamis, visit DNR’s Geology Division’s web site.

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