Coupling between the subducting Juan de Fuca plate and the overriding North America at the shallow-dipping Cascadia subduction zone (Crosson & Owens, 1987) is expected to cause future large earthquakes and tsunamis. Previous studies (Atwater, 1987;Goldfinger et al., 2017;Satake et al., 2003) show that the ∼1,100 km plate boundary extending from British Columbia to northern California has generated large tsunamis in the past. The tsunami from the most recent great Cascadia earthquake or sequence of events, with an inferred total magnitude of 9 (