Tsunami Inundation Modeling of Sequim Bay Area, Washington, USA from a Mw 9.0 Cascadia Subduction Zone Earthquake

Abstract

The Strait of Juan de Fuca and the coastline nearby are prone to tsunami attacks along the Cascadia Subduction Zone (CSZ). Besides the tsunami deposits that exist on the outer coast, the inland geological evidence shows that nine sandy-muddy Cascadia tsunami deposits intrude a 2500-yr-old sequence of peat deposits beneath a tidal marsh at Discovery Bay, Northern Olympic Peninsula, Washington (Williams et al., 2005). Thus, assessing the potential damage for the next CSZ earthquake tsunami event is important. In this study, I conducted tsunami simulations using the GeoClaw numerical model by a scenario earthquake. The earthquake scenario adopted for this study is a Mw 9.0 CSZ earthquake, also known as the “L1” scenario (Witter et al., 2011). Fine-resolution (1/3 arc-second) digital elevation models (DEMs) are used to provide high resolution tsunami inundation results on Sequim Bay area at northern Olympic Peninsula. The numerical gauges which are set around the major Infrastructure and properties provide information of wave height, wave velocity and wave arrival time. Four tsunami waves with 2-meter-height are found over the ten hours simulation. Also, two spits at the entrance of Sequim Bay can diminish and delay the tsunami impacts in the Bay. The modeling results will contribute to public safety administration in the Pacific Northwest as an aid to development of hazard mitigation plans and emergency response.