EVALUATION OF THE IMPORTANCE OF MODEL FEATURES FOR CYCLIC DEFORMATION DUE TO DIP-SLIP FAULTING

Finite-element techniques are used to investigate models of cyclic deformation on dip-slip faults. The models are based largely on the conceptual formulations of Matsu'ura and Sate (1989), Savage (1983), and Thatcher and Rundle (1984). We investigate the interaction of rheology, fault geometry, mechanical structure, non-tectonic forces, and the earthquake recurrence interval. The interaction of gravity and viscoelastic flow is complex. For example, if the asthenosphere is very weak, then regions that rise rapidly after an earthquake may subsequently subside due to isostatic readjustment. By contrast, if the asthenosphere is more viscous, uplifted regions may continue to grow throughout the earthquake cycle. The magnitude and width of regions of both uplift and subsidence depend on density, viscosity and viscoelastic channel thicknesses. The inclusion of plate bending appears to be important in earthquake modelling at subduction zones. The steady-state convergence of plates may lead to net vertical motion in the subduction zone.