Newly Published: Southwest Washington Tsunami Inundation Hazard Maps

We are pleased to announce the publication of new tsunami hazard maps for southwest Washington!

Tsunami Hazard Maps of Southwest Washington—Model Results from a ~2,500-year Cascadia Subduction Zone Earthquake Scenario

New finite-difference modeling along the southern Washington coast in the area surrounding Willapa Bay and Grays Harbor uses a simulated magnitude 9 earthquake event with a maximum slip of 88.6 feet (27 meters), inferred to be a ~2,500-year event, or the L1 scenario. Modeling results indicate that the first tsunami wave is projected to arrive on land along the outer coast in 15 to 20 minutes following the earthquake. Inundation depths range from 20 to 60 feet (6–18.2 meters) on the outer coast, decreasing to generally less than 10 feet (3 meters) within Willapa Bay and Grays Harbor. Current velocities from the tsunami waves locally exceed 35 knots, presenting a significant navigational hazard to the maritime community. Tsunami wave inundation is expected to continue over 12 hours and remain hazardous to maritime operations for more than 24 hours after the earthquake. This study is limited in that modeling does not account for tidal effects or minor topographic changes that would locally modify the impact of tsunami waves. Due to these limitations, this modeling should not be used for site-specific tsunami inundation assessment or for determining effects on the built environment. However, this model is an excellent tool for evacuation and recovery planning.


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Suggested Citation: Eungard, D. W.; Forson, Corina; Walsh, T. J.; Gica, Edison; Arcas, Diego, 2018, Tsunami hazard maps of southwest Washington—Model results from a ~2,500-year Cascadia subduction zone earthquake scenario: Washington Geological Survey Map Series 2018-01, 4 sheets, scale 1:48,000, 11 p. text.

Look for this new data set on our Geology Portal in the near future! In the meantime check out the Portal for more tsunami inundation maps for other locations along the Washington coast.