3-D Physical Modelling of Stress Accumulation Processes at Transcurrent Plate Boundaries

We constructed a 3-D physical model of tectonic loading at transcurrent plate boundaries by considering viscoelastic stress relaxation in the asthenosphere and spatial variation in frictional properties (peak strength and critical weakening displacement) of faults. With this model we simulated the process of stress accumulation and release at a seismogenic region with relatively high strength on the plate interface. In low strength regions surrounding the seismogenic region, quasi-static fault slip gradually proceeds with the progress of relative plate motion. The increase of slip deficits in the seismogenic region brings about stress concentration at its margin. The stress accumulation rate is roughly proportional to the inverse of the effective fault length. The accumulated stress is released by unstable dynamic rupture if the critical weakening displacement Dc is small, and by stable fault slip if Dc is very large. When a fault system consists of two adjacent seismogenic regions, sudden stress release in one region accelerates the stress accumulation process in another region through transient viscoelastic stress transfer as well as instantaneous elastic stress transfer. This indicates the importance of elastic and viscoelastic interaction between adjacent seismic faults even in stress accumulation processes.