Hydrodynamic Simulations of Historic Tsunamis from the Cascadia Subduction Zone

INTRODUCTION We use new geological and hydrodynamic models to simulate the sea floor deformation and tsunami runup and inundation in Cannon Beach, Oregon (Fig. 1) produced by Cascadia subduction zone (CSZ) earthquakes. We then compare the simulated inundation with inland extent of buried sand sheets inferred to be of tsunami origin. The CSZ exhibits similarities to other subduction zones around the world, particularly the Sunda-Andaman subduction zone. We therefore used the 2004 Indian Ocean earthquake and tsunami to partially guide the design of fault source models. Given the large uncertainties and natural variation possible in the deformation caused by the earthquakes, our main aim here is to minimize these uncertainties and explore the variability by considering multiple geological and geophysical constraints so that meaningful hydrodynamic simulations can be carried out. Therefore we use an ensemble of plausible fault models to test our hypotheses on the past earthquake events, and derive the most likely scenario by comparing the wave runup and maximum inundation as calculated by the model against field observations of extensive sand sheets inferred to record prehistoric tsunami inundation.