Application of three fault growth criteria to the Puente Hills thrust system, Los Angeles, California, USA

Abstract

Three-dimensional mechanical models are used to evaluate the performance of different fault growth criteria in predicting successive growth of three échelon thrust faults similar to the segments of the Puente Hills thrust system of the Los Angeles basin, California. Four sequential Boundary Element Method models explore the growth of successive échelon faults within the system by simulating snapshots of deformation at different stages of development. These models use three criteria, (1) energy release rate, (2) strain energy density, and (3) Navier–Coulomb stress, to characterize the lateral growth of the fault system. We simulate the growth of an échelon thrust fault system to evaluate the suitability of each of these criteria for assessing fault growth. Each of these three factors predicts a portion of the incipient fault geometry (i.e. location or orientation); however, each provides different information. In each model, energy release rate along the westernmost (leading) tip of the Puente Hills thrust drops with growth of the next neighboring fault; this result supports the overall lateral development of successive échelon segments. Within each model, regions of high strain energy density and Navier–Coulomb stress envelope at least a portion of the next fault to develop, although the strain energy density has stronger correlation than Navier–Coulomb stress to the location of incipient faulting. In each model, one of the two predicted planes of maximum Navier–Coulomb stress ahead of the leading fault tip matches the strike but not the dip of the incipient fault plane recreating part of the fault orientation. The incipient fault dip is best predicted by the orientation of the strain energy density envelopes around the leading fault tip. Furthermore, the energy release rate and pattern of strain energy density can be used to characterize potential soft linkage (overlap) or hard linkage (connection) of échelon faults within the system.