Distinct asymmetry in rupture-induced inelastic strain across dipping faults: An off-fault yielding model

Abstract

Off-fault stresses associated with rupture propagation cause material yielding under a Mohr-Coulomb condition, leaving irrecoverable deformation in the fault zone. 2D dynamic rupture simulations for a 30° reverse fault and a 60° normal fault in a depth-dependent stress environment show that the yielding (inelastic) zone off the fault broadens as it nears the surface with decreasing confining pressure, forming a skewed 'flower-like' structure bounded at the top by the free surface. The inelastic strain in the hanging wall is significantly larger and broader than the footwall for both reverse and normal faults. The occurrence of inelastic strain, however, significantly reduces ground motion (especially on the hanging wall) and gives rise to a reduced asymmetry in ground motion on the hanging wall and footwall compared to elastic solutions. These results provide theoretical predictions for fault zone structure of dipping faults that can be tested by future observational experiments. Copyright 2009 by the American Geophysical Union.