The Effects of d₀ on Rupture Propagation on Fault Stepovers

According to the slip‐weakening friction law (Andrews, 1976a), fault friction drops from a static value to a sliding value over some slip‐weakening distance (d₀). Laboratory studies of fault friction confirm this weakening, but do not settle on a single value for d₀. However, this parameter is a critical input in dynamic earthquake models, as it affects rupture nucleation and propagation. We use the 2D finite‐element method to test how the specific value of d₀ affects rupture behavior. We consider the ability of rupture to jump from segment to segment of a disconnected stepover, or to propagate through the double bends of a connected stepover, as a way to gauge rupture energy and behavior. We find the stepover width or bend angle through which rupture can propagate is affected by the choice of d₀, but it is not a linear relationship. This is true regardless of whether the stepover is connected or disconnected, compressional or extensional, or whether the initial rupture velocity is supershear or subshear. We do find, however, that scaling the intensity of the regional stress field up or down does linearly correspond to scaling d₀ down or up. We interpret the nonlinearity of the d₀ scaling results to be related to the area of the secondary fault that intersects the lobe of failure‐level Coulomb stress change induced by rupture of the first fault segment because (1) the d₀‐controlled critical patch size for renucleation must be exceeded on the second segment and (2) the area of this overlap also does not change linearly with distance from the first fault.