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January AEG Dinner Meeting

Topic: Tsunamis past and future: tsunami deposits and simulations along the Salish Sea coastline of Washington State

Speaker: Carrie Garrison-Laney – University of Washington

Time: 5:30 – Social Hour

6:30 – Dinner

7:30 – Presentation

Place: Best Western Executive Inn, 200 Taylor Avenue North, Seattle, WA 98109, 206-448-9444

Presentation Abstract:

The Salish Sea inner coastline of Washington State, which includes the urban waterfronts of Seattle, Tacoma, and Everett, has tidal marshes that record past tsunamis as anomalous sand layers in peaty marsh deposits. While Washington has other tsunami sources, Cascadia tsunamis are the most likely source of deposits from tidal marsh sites at Discovery Bay on the Strait of Juan de Fuca, and at Lynch Cove at the head of Hood Canal. GeoClaw simulations of four different Cascadia tsunamis show wave amplification at both sites, while simulations of tsunamis from the Seattle fault does not. Simulations of an Alaska-Aleutian tsunami predict flooding at both sites, but high-resolution radiocarbon ages of the deposits agree best with land and marine records of Cascadia earthquakes. The tsunami history along Washington’s inner coastline continues to be refined with new geologic evidence from additional sites, and the hazards are becoming better understood through new high-resolution tsunami modeling of the Mw 9.0 “L1” Cascadia earthquake scenario. The L1 is a hypothetical earthquake with a surface-rupturing splay fault that amplifies tsunami generation, and is currently being used for the next generation of tsunami inundation maps in Washington State. These maps will identify areas with the greatest hazard, and will be important for the maritime community, shoreline planning, and coastal risk assessment.

Speaker Bio:

Dr. Carrie Garrison-Laney is a tsunami hazards expert at Washington Sea Grant and liaison to the National Center for Tsunami Research at the Pacific Marine Environmental Laboratory in Seattle. Her graduate research focused on paleotsunami deposits at intertidal marsh sites around the Salish Sea, and included numerical modeling of tsunamis, a study of marine and intertidal diatom evidence for tsunami and sea level change, and radiocarbon dating of the timing of inundation events. Carrie’s interests include tsunami science, scientific communication, and education. Carrie participates in a variety of outreach activities, including Washington’s annual Tsunami Roadshow. She has earned a bachelor’s degree in Geosciences from San Francisco State University; a master’s degree in Environmental Systems from Humboldt State University; a master’s degree in Human Centered Design and Engineering from the University of Washington; and a Ph.D. in Earth and Space Sciences from the University of Washington.

Earlier Event: December 12
December AEG Holiday Party
Later Event: February 21
February AEG Dinner Meeting