Modeling of periodic great earthquakes on the San Andreas Fault: effects of nonlinear crustal rheology

The cycle of great earthquakes along the San Andreas fault is analysed with a finite element numerical model of deformation in a crust with a nonlinear viscoelastic rheology. The results are sensitive to crustal rheology. Models with quartzite-like rheology display profound transient stages in the velocity, displacement, and stress fields. The predicted transient zone extends about 3-4 times the crustal thickness on each side of the fault. Models with diabase-like rheology behave similarly to elastic models and exhibit no transient stages. The model predictions are compared with geodetic observations of fault-parallel velocities in northern and central California and local rates of shear strain along the San Andreas fault. -from Authors