Tsunami refuge planned on state’s coast

Tsunami zone near Westport and Grayland Beach
Light blue shows the areas of the Washington coast between Westport and Grayland that would be inundated by a tsunami resulting from a large earthquake in the Cascadia Subduction Zone. CLICK graphic to enlarge.

One of the first large tsunami refuges in the U.S. will be built in Washington State. And why not? Just off our coastline is the Cascadia Subduction Zone—a 700-mile-long offshore fault where tectonic plates meet. It is capable of producing earthquakes and tsunamis as large as the ones that pummeled northern Japan in 2011, also caused by an earthquake along an undersea subduction zone. The odds of a 9.0 magnitude earthquake in the Cascadia zone in the next 50 years are about one in 10, according to the Cascadia Region Earthquake Workgroup.

With these risks in mind, residents of Westport and other communities in the Ocosta School District last year approved a $13.8 million bond issue to replace an aging elementary school and build a gymnasium that will double as the nation’s first tsunami refuge structure.

Located less than a mile from the ocean, the school and much of the surrounding community are in the path of the likely tsunami surge from a large earthquake on the Cascadia zone. The new gym’s roof will sit about 55 feet above sea level, well above the highest surges predicted for the school site.

DNR geologists were among the experts who advised local officials and participated in public workshops with residents about tsunami dangers in Westport and other at-risk communities on Washington’s outer coast. Elevated refuges can be the most practical and affordable options to survive a tsunami in communities where rapid evacuation is not possible. Many of the people killed in the 2011 tsunami in northern Japan received warning but could not flee fast enough or reach a high-enough area to avoid the deadly waves created by a 9.1 magnitude earthquake.

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