Theory of plasticity applied to faulting, Mojave Desert, southern California

Abstract

The Mojave Desert region, a triangle-shaped area in southern California, is bounded on the northwest by the left-slip Garlock fault and on the southwest by the right-slip San Andreas fault. Within the triangle partly defined by these two faults, right-slip northwest-trending and left-slip northeast-trending faults occur. The structural geology and fault pattern within the triangle are uniform and internally consistent and are markedly different from the structural geology and fault pattern of the areas to the north and south. To describe the pattern of faults and to interpret the mechanics of deformation of the triangle, a two-dimensional model from theory of plasticity is proposed wherein an analogy is made between the Mojave Desert triangle and L. Prandtl9s compressed cell. To simulate regional stresses, the cell is subjected to north-south compression. The maximum shear-stress trajectories developed in the theoretical model have the same orientation and sense of relative movement as the faults in the Mojave Desert area. The theoretical model may be used to predict the orientations and sense of movement along faults that might form in the future.