San Andreas fault geometry through the San Gorgonio Pass, California

Abstract

Three-dimensional numerical models are needed to investigate the role of nonvertical strike-slip fault segments on the deformation within restraining bends. Numerical models simulate geologic deformation of two alternative three-dimensional present-day configurations for the San Andreas fault through the restraining bend within the San Gorgonio Pass region (SGPR) in Southern California. Both models produce decreasing strike-slip rates southward along the San Bernardino strand of the San Andreas fault, similar to geologic data. The north-dipping San Andreas fault model better matches the available strike-slip data as well as the geologic uplift data for the southern San Bernardino Mountains than the vertical San Andreas fault model. We conclude that a north-dipping fault configuration is preferred for models of the San Andreas fault in the SGPR. The complexity of the active fault geometry at the SGPR promotes the transfer of strike slip from the San Andreas fault to the nearby but unconnected San Jacinto fault. Slip rates and uplift patterns are sensitive to fault geometry within strike-slip restraining bends.