Energy driven fault growth in a layered medium

We model the crack growth in an elastic medium constituted by two welded half-spaces with different rigidities. We implement a 2-D boundary element method computing shear and normal tractions acting on the crack and the slip accommodating stress drop. The direction of crack growth follows the criterion of maximum energy release (strain and gravitational energy) provided that it overcomes the surface fracture energy and the work dissipated by friction. The model simulates complex fault geometries and it explains the change of dip angles for both normal and reverse faults, when they enter layers with different rigidities