The cascading impacts of megathrust earthquakes: Connecting ground shaking and tsunamis in the Cascadia Subduction Zone – Audrey Dunham (USGS), Erin Wirth (USGS), Randy LeVeque (UW), Yong Wei (UW)

The Cascadia Subduction Zone (CSZ) is anomalously quiet, with a dearth of moderate-to-large magnitude seismicity in the instrumented record. However, paleoseismic evidence indicates that the CSZ ruptures in large (~M8-9) megathrust earthquakes, with the last great event occurring in 1700. Along with strong shaking that could last on the order of minutes, these earthquakes cause the seafloor to uplift, displacing the water column and generating tsunami waves that will impact the many communities that populate the Pacific Northwest coast. Without instrumental recordings of earthquake shaking or past tsunamis, we turn to simulations of these natural hazards to quantify their impacts and help communities better prepare. In this talk, CoPes Hub earthquake and tsunami researchers will outline recent work being done to develop new ground shaking and tsunami simulations of Cascadia megathrust earthquakes to better understand the time dependent impacts of these cascading hazards. The preliminary tsunami simulations highlight the variation of possible tsunamis that arise from these new ground motions and the existence of localized hotspots of tsunami energy focusing along the Pacific Northwest coast.