11:15 AM - 11:30 AM
[S13-6-04] Modeling dynamic earthquake rupture with coseismic off-fault damage
Off-fault stress concentration induced by dynamic earthquake ruptures can generate coseismic off-fault damage, which has an effect on source mechanisms of earthquakes. We need continuum-discontinuum analysis to understand the process of generating the off-fault damage in a brittle material surrounding faults and the role of it in the source mechanisms and seismic wave radiation.
In this study, we adopt combined finite-discrete element method (FDEM), which can model real cracks in off-fault fields generated during the dynamic earthquake ruptures. The advantage of FDEM is that it can handle a wide range of length scales, from metric to kilometric scale, corresponding to the off-fault damage and the main fault respectively. Every potential failure plane in the medium follows a cohesive law (in tension and in shear). The main fault is assumed to follow a linear slip-weakening friction. Thus we can have an estimate of fracture energy dissipated on the main fault and the off-fault damage separately. We used the FDEM-based software tool called HOSSedu (Hybrid Optimization Software Suite - Educational Version), which was developed by Los Alamos National Laboratory.
We firstly demonstrated the cross-validation of the FDEM tool for modeling earthquake ruptures with other conventional numerical schemes like spectral element method and boundary integral equation method to evaluate the accuracy with various element sizes and artificial viscous damping factors. We then modeled earthquake ruptures allowing for the coseismic off-fault damage with appropriate fracture nucleation and growth criteria. It shows that high-frequency radiation is enhanced by the dynamically generated off-fault damage. The orientation of maximum compressive principal stress of the pre-stress field with the main fault plays a role in generating the off-fault damage such that the dynamic off-fault damage is more likely to occur on the extensional side of the main fault for high principal stress orientation.
In this study, we adopt combined finite-discrete element method (FDEM), which can model real cracks in off-fault fields generated during the dynamic earthquake ruptures. The advantage of FDEM is that it can handle a wide range of length scales, from metric to kilometric scale, corresponding to the off-fault damage and the main fault respectively. Every potential failure plane in the medium follows a cohesive law (in tension and in shear). The main fault is assumed to follow a linear slip-weakening friction. Thus we can have an estimate of fracture energy dissipated on the main fault and the off-fault damage separately. We used the FDEM-based software tool called HOSSedu (Hybrid Optimization Software Suite - Educational Version), which was developed by Los Alamos National Laboratory.
We firstly demonstrated the cross-validation of the FDEM tool for modeling earthquake ruptures with other conventional numerical schemes like spectral element method and boundary integral equation method to evaluate the accuracy with various element sizes and artificial viscous damping factors. We then modeled earthquake ruptures allowing for the coseismic off-fault damage with appropriate fracture nucleation and growth criteria. It shows that high-frequency radiation is enhanced by the dynamically generated off-fault damage. The orientation of maximum compressive principal stress of the pre-stress field with the main fault plays a role in generating the off-fault damage such that the dynamic off-fault damage is more likely to occur on the extensional side of the main fault for high principal stress orientation.