Construction of equivalent single planar fault model for strike-slip stepovers

Non-planarity is a common and natural characteristic of seismic faults that strongly affects the rupture dynamics and the associated seismic waves. Geometrically uniform planar fault model is widely used in studies of kinematic source inversion, seismic hazard estimation and rupture dynamic simulation because of the simplicity and computational efficiency of this method. The influence of the geometric heterogeneity of faults on rupture dynamics and associated seismic waves may under some circumstances be reasonably approximated by an appropriate heterogeneous distribution of shear strength of planar faults, particularly for the case with uniform initial stress distribution. An outstanding issue is how to approximate the dynamic behavior of a non-planar fault by means of heterogeneous properties on a planar fault. Thus, we propose the construction of an equivalent planar fault model for a given stepover fault through the introduction of a heterogeneous distribution of static friction coefficient. Our study shows that the distribution of static friction coefficient on the equivalent planar fault model is mainly controlled by the geometric irregularities of the stepovers regardless of the initial shear stress, thereby providing a way to quantify the effect of fault geometry, particularly the step width effect in seismic hazard estimation. Moreover, our results indicate that the influence of geometric discontinuity of stepovers on rupture dynamics is equivalent to a barrier of the planar fault model.