Character of slip and stress due to interaction between fault segments along the dip direction of a subduction zone

We have performed a two-dimensional numerical simulation to elucidate the physical processes governing earthquake behavior when significant stress perturbations are produced by interaction between fault segments. Our model involves two seismogenic segments separated down-dip on a subduction zone plate boundary and incorporates a rate- and state-dependent friction law. Based on repeated simulations under different scenarios, we find that the rate- and state-dependent frictional parameters (b-a) and d_c in the deeper seismogenic segment are required to be smaller than those in the shallower segment in order that more deep earthquakes occur than shallow ones. Our simulations show that slip amounts in either seismogenic segment increase in each of the co-, pre- and post-seismic stages when an earthquake occurs shortly after another earthquake in the other seismogenic segment. Conversely, when earthquakes occur in a single seismogenic segment several times in succession while the other segment remains locked, all three pre-, co-, and post-seismic slip amounts become smaller. These results imply that precursory changes do not necessarily occur at the same level on every occasion. In cases of multiple rupturing, the co-seismic slip of the later earthquake in a pair is approximately characteristic when frictional stability in the aseismic segment between the two seismogenic fault segments is strong enough to produce different rates of seismicity on each segment. Our simulation also shows that the degree to which rupture initiation points vary between different earthquakes is higher in low seismic coupling regions. This result may prove useful in estimating seismic coupling coefficients from observations of interplate hypocenters.