We numerically investigate the role of plastic strain accumulation on
the mechanical response of a planar strike-slip fault. Our models show
that fault-zone strength significantly impact the ensuing sequence of
earthquakes. Weaker fault zones accumulating more plastic strain promote
more complexity in the seismicity pattern through aperiodic earthquake
occurrences and intermittent episodes of rupture and arrest. However, if
the fault zone strength is high enough, the overall earthquake sequence
is characterized by periodic fault-spanning events. We find that both
the fault normal stress and the fault surface profile evolve throughout
the earthquake sequence, suggesting a self-roughening mechanism. Despite
the significant impact of plasticity on the fault response, the width of
the plastically deforming region in the fault zone is small compared to
the fault length. Our results suggest a rich behavior in dynamically
evolving fault zones and support the need for further high-resolution
studies of the highly non-linear near-fault region.