Newly Published: Port Angeles and Port Townsend Tsunami Inundation Hazard Maps

We are pleased to announce the publication of new tsunami hazard maps for Port Angeles and Port Townsend!

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Tsunami hazard maps of Port Angeles and Port Townsend, Washington—Model Results from a ~2,500-year Cascadia Subduction Zone Earthquake Scenario

New tsunami modeling along the Strait of Juan de Fuca within an area surrounding the communities of Port Angeles and Port Townsend uses a simulated magnitude 9 earthquake event along the Cascadia subduction zone (L1 scenario) with a maximum slip of ~89 ft (27 m), inferred to be a ~2,500 year event. This new Cascadia subduction zone earthquake scenario aims to approximate the seismic design requirements in the building code standard for critical facilities, and the tsunami modeling is more conservative (greater inundation) than previous models. Modeling results indicate that sea level immediately following the earthquake gradually recedes to a maximum drawdown of ~6.5 ft (2 m) before the first tsunami wave arrival. This first wave is projected to inundate as high as 21 ft (6.4 m) locally in Port Angeles and Port Townsend approximately 60 minutes and 100 minutes respectively following the earthquake. Current velocities from the tsunami waves locally approach 26 knots, presenting a significant navigational hazard to the maritime community. Tsunami wave inundation is expected to continue over 8 hours and remain hazardous to maritime operations for more than 24 hours. This study is limited in that modeling does not account for tide stage, tidal currents, liquefaction, or minor topographic changes that would locally modify the effects 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 appropriate tool for evacuation and recovery planning.

Suggested Citation: Eungard, D. W.; Forson, Corina; Walsh, T. J.; González, F. I.; LeVeque, R. J; Adams, L. M., 2018, Tsunami hazard maps of Port Angeles and Port Townsend, Washington—Model results from a ~2,500-year Cascadia subduction zone earthquake scenario: Washington Geological Survey Map Series 2018-03, 6 sheets, scale 1:11,000 and 1:16,000, 11 p. text.

[http://www.dnr.wa.gov/publications/ger_ms2018-03_tsunami_hazard_pt_angeles_pt_townsend.zip]

Look for these new data sets on our Geology Portal in the near future! In the meantime check out the Portal for more tsunami inundation maps of other places along the Washington Coast.