Stress perturbations registered by jointing near strike-slip, normal, and reverse faults: Examples from the Ebro Basin, Spain

Abstract

Stress perturbation patterns created by coeval and preexisting fault planes are characterized by means of detailed mapping and analysis of joint sets in Miocene carbonates of the Tudela area. Strike and spacing of the pervasive N-S joint set have been specially surveyed for this purpose; their spatial variations have been analyzed and interpreted in the light of different theoretical models proposed by other authors. Perturbations inferred near strike-slip faults correspond to the classical examples related to compressional and extensional fault tips. A normal fault striking oblique to the horizontal stress axes deflects the latter toward making σ2 and σ3 trajectories parallel and perpendicular, respectively, to the fault strike, while causing an abrupt stress release within the footwall. Near a reverse fault with a small dextral component the deflection of σ1 trajectories is gentle, but a significant increase of differential stress occurs in the hanging wall. Copyright 1999 by the American Geophysical Union.