Interaction between normal faults and fractures and fault scarp morphology

Abstract

Fault slip and geomorphic surface processes create and modify bedrock normal fault scarps. Our field studies and numerical models show that mechanical interaction between near‐surface fractures and active faults may diminish scarp slopes and broaden deformation near the surface. In our models, increasing fracture density and depth reduces and complicates the scarp's topographic expression. Fracture depth and density, and orientation of the structures control the location and magnitude of zones of positive and negative shear displacements along the fractures. Our field studies of the interaction of active graben bounding normal faults and fractures in Northern Arizona illustrate the mechanical analysis. Reduction in scarp slopes and broadening of the deformation field may cause incorrect interpretations of shallow bedrock scarp morphologies as old, rather than as the result of slip along fractures around the fault.