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Date of Award
Department or Program Affiliation
Master of Science (MS)
Housen, Bernard Arthur
Grossman, Eric E.
The Cascadia subduction zone is understood to produce large, Mw 9.0, earthquakes every 300-1000 years. As a result of large ruptures along the fault, Washington, Oregon and Northern California, are susceptible large tsunamis along the coast. Hazard modeling and mapping along the Cascadia subduction zone has concluded that large tsunamis are able to travel through the Strait of Juan de Fuca and inundate coastal regions of the Salish Sea and Puget Sound. However, to improve modeling efforts, field validation of models is required. Tsunamis can move material from the near shore and beach and deposit in low-laying coastal marshes and ponds, acting as a proxy for past tsunami inundation. This research focuses on two locations in the northern Puget Sound, Ship Harbor marsh Anacortes, and Eliza Island. Using gouge auger cores and vibracores, subsurface features of each marsh were reconstructed to look for laterally continuous sand sheets indicative of tsunami inundation. Magnetic methods were used to correlate between cores, and look at sedimentary depositional fabrics within stratigraphic beds. Potential Cascadia tsunami origin for a deposit at Ship Harbor was confirmed with the use of 14C dates and magnetic paleosecular variation dates. This research has implications for validation of the L1 seismic-scenario-based tsunami models, currently being produced by the Washington Geological Survey for hazard planning, and may indicate that L1 based tsunami models are valid regarding the inundation threat along the inland coast for future Cascadia earthquakes.
Tsunami, sedimentology, stratigraphy, coastal, deposition, Ship Harbor, tsunami deposit, tsunami deposition, model validation, coastal geology, sediments, paleosecular variation dating, sedimentary fabrics
Western Washington University
Subject – LCSH
Tsunamis--Northwest, Pacific; Tsunami hazard zones--Northwest, Pacific; Earthquake hazard analysis--Northwest, Pacific; Earthquakes--Northwest, Pacific; Geology, Structural--Northwest, Pacific; Tsunami hazard zones--Washingon (State)--Puget Sound; Tsunami hazard zones--Washington (State)--Anacortes; Tsunami hazard zones--Washington (State)--Eliza Island; Tsunami hazard zones--Salish Sea (B.C. and Wash.)
Cascadia Subduction Zone; Puget Sound (Wash.); Anacortes (Wash.); Eliza Island (Wash.); Salish Sea (B.C. and Wash.)
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Morkner, Paige, "Validation of Predicted Tsunami Inundation for the Inland Coast of the Salish Sea Associated with Cascadia Subduction Zone Earthquakes" (2019). WWU Graduate School Collection. 895.