Three Dimensional Dynamic Earthquake Rupture Simulations of the Cascadia Subduction Zone Incorporating Its Along-Strike Variation in the Fore-Arc Deformation Style

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: 

A recent study (Han et al., 2017) used active-source seismic and ocean drilling data to constrain the sediment consolidation near the deformation front of the Cascadia subduction zone (CSZ). The study particularly focused on two cross-margin transects sampling Washington region and central Oregon region and suggested along-strike variations in the fore-arc deformation style of the CSZ. The northern fore-arc wedge of the CSZ is marked by landward-vergent thrust faults, while on the south, the thrust faults are mainly seaward-vergent. To better understand how the along-strike variation of the fore-arc deformation style of the CSZ may contribute to the seismic hazard of the region, we perform 3D dynamic earthquake rupture simulations of a fault system, similar to the CSZ, while incorporating along-strike variation in fore-arc deformation style. Our model consists of a long shallow dipping plate boundary thrust (oriented north-south) with steep dipping splay faults that are oriented in opposite directions. We vary earthquake nucleation location and pre-stress conditions along the strike of plate boundary thrust to assess scenarios that may lead to activation of the splay faults. Our preliminary results suggest that the rupture mostly stays at the plate boundary thrust, while fewer set of initial conditions can activate the splay fault. Additionally, we also perform surface deformation modeling with its initial conditions derived from our dynamic earthquake rupture model to investigate the post-rupture evolution of the sea floor bathymetry. We do this is to identify any distinct sea floor bathymetric features that may be associated with a paleo mega-thrust subduction event and hence can provide insights into the rupture behavior of that event.

Presenting Author: Khurram Aslam

Authors