Characterization of stress perturbations near major fault zones: insights from 2-D distinct-element numerical modelling and field studies (Jura mountains)

We consider and discuss the presence of discontinuities in the crust as a major source of stress perturbations. Based on 2-D distinct-element modelling, we reconstruct the local stress field around a vertical discontinuity in various geological contexts. The resulting stress distribution reveals that major directional stress changes occur near the tips of the discontinuity so that stress deviations can reach values as large as 50 °. We establish simple relationships controlling stress changes around a pre-existing fault zone as a function of (1) the remote differential stress magnitude, (σ1 − σ3), (2) the friction coefficient on the discontinuity, and (3) the strike of the discontinuity relative to the far-field stress. eological example, we present the Morez Fault Zone in the internal Jura. Paleostress reconstruction in forty-two sites indicates that the trends of the Mio-Pliocene compression are N110 ° on average near the fault, whereas they are N130 ° in the surrounding areas. A comparison between the results of the tectonic study and those of theoretical modelling suggests that the 20 ° counterclockwise deviation is directly related to the reactivation of this large weak zone. We thus evaluate the role of mechanical decoupling along pre-existing zones of weakness, especially with consideration to the accommodation of the Alpine deformation in the Jura belt.