Rupture propagation beyond fault discontinuities: significance of fault strike and location

Earthquake rupture sometimes occurs on several faults, and often decelerate s or terminates at fault stopovers. Factors that control the rupture proces ses across stopovers are important for an understanding of earthquake growt h and termination. In this study, we investigate such factors by calculatin g the spontaneous rupture processes of two non-coplanar faults in a 3-D mod el. Dealing with two extreme models in which two strike-slip faults are eit her parallel or perpendicular, we show that the rupture processes beyond fa ult discontinuities are drastically different for the two models. We find t hree factors influencing rupture processes beyond fault discontinuities: de pth of the upper edge of the two faults, location of the edge of the first fault and geometry of the two faults. These factors determine the time and location of rupture jumps to the second fault. For rupture propagation to t he second fault, it is essential for rupture on the first fault to arrive a t the edge of the fault. In particular, whether rupture on the first fault reaches the Earth's surface or not controls the difficulty of rupture jumps and the locations where the rupture is triggered, which is also related to the step direction of the two faults. This is because the stress perturbat ion at the fault edge is affected by the Earth's free surface.