Impacts of off-fault plasticity on fault slip and interaction at the base of the seismogenic zone
Direct observations of faults exhumed from mid-crustal depths indicate that distributed inelastic deformation enhances fault slip and interaction across steps. Constrained by field measurements, finite element models demonstrate that the slip distribution for a fault in a Mises elastoplastic continuum differs significantly from that of a linear elastic model fault. Lobes of plastic shear strain align with fault tips and effectively lengthen the fault, resulting in greater maximum slip and increased slip gradients near fault tips. Additionally, distributed plastic shear strain facilitates slip transfer between echelon fault segments. Fault arrays separated by contractional steps, which are subjected to greater mean normal stress and Mises equivalent stress, produce greater maximum slip than do those separated by extensional steps (with no fractures). These results provide insight into fault behavior at the base of the seismogenic zone, with implications for rupture dynamics of discontinuous faults.