The role of bed-parallel slip in the formation of blind thrust faults

Abstract

A finite-element code is used to model the mechanical behaviour of elastoplastic sedimentary layers that are deformed by the movement of a faulted, deformable basement. The propagation of the blind thrust fault is analysed in terms of the evolution of strain localization in the elastoplastic layers of strain-softening and strain-hardening materials. The role of layer thickness, bedding-parallel slip, and fault dip are also studied. We found that, if no interlayer slip is allowed, blind thrusts tend to propagate with constant dip, regardless of the rheological properties of the sediment layers; however, if bedding-parallel slip is present, a mechanical decoupling appears between layers, allowing stress transfers along large distances and favouring the formation of backthrusts. Fault dip also has significant influence on the qualitative behaviour; when interlayer slip is possible, a steep fault will tend to split.