THE ROLE OF BED-PARALLEL SLIP IN THE FORMATION OF BLIND THRUST FAULTS

A finite-element code is used to model the mechanical behaviour of ela stoplastic sedimentary layers that are deformed by the movement of a f aulted, deformable basement. The propagation of the blind thrust fault is analysed in terms of the evolution of strain localization in the e lastoplastic layers of strain-softening and strain-hardening materials . The role of layer thickness, bedding-parallel slip, and fault dip ar e also studied. We found that, if no interlayer slip is allowed, blind thrusts tend to propagate with constant dip. regardless of the rheolo gical properties of the sediment layers; however, if bedding-parallel slip is present, a mechanical decoupling appears between, lapels, allo wing stress transfers along large distances and favouring the formatio n of backthrusts. Fault dip also has significant influence on the qual itative behaviour; when inter layer slip is possible, a steep Fault wi ll tend to split. (C) 1998 Elsevier Science Ltd. All rights reserved.