Cascadia Earthquake and Tsunami Scenarios Based on 3D Dynamic Rupture Simulations

Session: Exploring Rupture Dynamics and Seismic Wave Propagation Along Complex Fault Systems [Poster]
Type: Poster
Date: 4/29/2020
Time: 08:00 AM
Room: Ballroom
Description: 

Predicting future ground shaking and crustal deformation generated by megathrust earthquakes requires a physically consistent source model that incorporates all available seismic, geologic and geodetic constraints. To this end, we present dynamic earthquake rupture models for the Cascadia megathrust that demonstrate how assumptions about the state of locking influence along-strike and along-dip rupture propagation. We explore how coseismic subsidence measurements from the 1700 A.D. megathrust event can be reproduced by honoring realistic topography and fault geometries in conjunction with fault physics (friction, strength and stress).

Major unknowns for the next Cascadia megathrust earthquake include where it will initiate, what conditions are dynamically favorable for a magnitude ~9 earthquake to develop and what a tsunami generated from slip near the deformation front may look like. To address these questions, we present several simulations that assume end-member recurrence interval periods from offshore turbidite analyses and show the sensitivity of nucleation location, stress drop amplitude and fault curvature to the final seismic moment. We then discuss the implications of our modeling in the context of interseismic (episodic tremor and slow-slip) and paleogeodetic observations that suggest spatial and temporal megathrust segmentation. Additionally, our tsunami simulations using these scenarios indicate that worst-case tsunami hazard is not unique to the largest rupture. This phenomenon results from coastal geometry and rupture slip distribution and has important implications for tsunami hazard mitigation.

By combining the latest constraints on Cascadia source dynamics with state-of-the-art modeling tools (i.e., SeisSol) we aim to contribute updated earthquake and tsunami scenarios for the Pacific Northwest.

Presenting Author: Marlon Ramos

Authors