A 3D Finite Element Dynamic Earthquake Simulator for Multicycle Dynamics of Geometrically Complex Faults Governed by Rate- and State-Dependent Friction

Dunyu Liu, & Benchun Duan

In Preparation May 4, 2019, SCEC Contribution #9070

We develop a finite element dynamic earthquake simulator to model multicycle dynamics of three-dimensional geometrically complex faults. The fault is governed by the rate- and state-dependent friction (RSF). The simulator integrates an existing finite element code EQdyna for the co-seismic dynamic rupture phase and a newly developed finite element code EQquasi for the quasi-static phases of earthquake nucleation, post-seismic and inter-seismic deformation of an earthquake cycle. Both finite element codes are parallelized through MPI to improve computational efficiency and capability. EQdyna and EQquasi are coupled through on-fault physical quantities of shear and normal stresses, slip-rates and state variables in the RSF. The simulator can handle time steps ranging from hundredths of a second to a fraction of a year based on a variable time stepping scheme, and can resolve the cohesive zone at rupture fronts of dynamic ruptures. The simulator is used to model multicycle dynamics of a 3D strike-slip fault with a bend. Complex earthquake event patterns are identified and the earthquake sequence presents two phases. In the first phase, there are three types of dynamic ruptures: ruptures breaking the whole fault from left to right, ruptures being halted by the bend, and ruptures breaking the whole fault from right to left. As the fault bend experiences more ruptures, the zone of stress heterogeneity near the bend widens and the earthquake sequence enters phase 2 showing only repeated ruptures that break the whole fault from left to right.

Citation
Liu, D., & Duan, B. (2019). A 3D Finite Element Dynamic Earthquake Simulator for Multicycle Dynamics of Geometrically Complex Faults Governed by Rate- and State-Dependent Friction. Geophysical Journal International, (in preparation).