Zone of weakness concept: a review and evaluation

Abstract

The zone of weakness concept implies that there exist within the earth's crust relatively weak zones which when differentially stressed will fail more readily than will the surrounding rock. Such zones are often inferred to determine the extent, orientation and style of younger deformation. Basement fabric elements which have been inferred to produce weak zones include faults, joints, foliation, cleavages, folds, shear zones, plate sutures, lithologic discontinuities, and basement terrane boundaries. Within this array of fabric elements one must consider a multiplicity of potential operating mechanisms. Each is conditioned by one or more environmental factors. Experimental deformation of basement rocks reveals complex relationships and mechanisms. Reactivation of some structures is well-established by field studies, but control of younger structures by older fabric anisotropies is not. -from Author