Heterogeneous fault stresses from previous earthquakes and the effect on dynamics of parallel strike-slip faults

[ 1] We combine a viscoelastic model for the interseismic process and an elastodynamic model for the coseismic process to explore the dynamics ( over multiple earthquake cycles) of two parallel strike-slip faults embedded in a two-dimensional full space. The step over fault geometry results in a buildup of heterogeneous fault stress near the step over. This heterogeneous stress accumulates at the early stage of the evolution of the fault system, and finally stabilizes after a number of earthquake cycles. The heterogeneity in fault stress varies with the geometrical parameters ( e. g., width and along-strike overlap/ gap) of the step over, as well as the rupture history of the fault system. This heterogeneous fault stress from previous earthquakes has significant effects on earthquake rupture initiation, propagation, and termination. The locations with a low normal stress level near a step over are favorable points for earthquake initiation. Rupture can jump a 4 km wide compressional step over and a 8 km or wider dilational step over if the fault system has historically experienced many earthquakes. A young step over with less induced heterogeneity allows rupture to jump only smaller step over widths. These results may have important implications for seismic hazard analysis in areas where segmented strike-slip faults predominate, particularly for estimating maximum earthquake potential.