FRICTIONAL AND GRAVITATIONAL EFFECT ON FAULT REACTIVATION: A MINIMUM-WORK APPROACH

Minimum-work methods have been used successfully in the past to study mountain building processes, including those that involve the generation of discrete faults and topography (i.e. thrust systems). The minimum-work hypothesis for the generation of mountain belts by compressional faulting assumes that the path of the individual fault that slips (active) is the one that involves the least mechanical work among all possible paths. Therefore, the orientation of a fault within a homogeneous and isotropic rock mass subjected to compression is a function of the mechanical properties (i.e. internal friction coefficient and fluid pressure) and the topography that is generated during deformation (overburden stress). In this study, we apply minimum-work principles, using analytical solutions, to thrust systems where preexisting weaknesses occur (i.e. preexisting faults) and different coefficients of sliding friction are present. We then compared the analytical to the numerical solutions derived from the Gale numerical code to contrast the results from both approaches using very similar modeling conditions (i.e. material properties and boundary conditions).This model setup provides an opportunity to test the controlling factors of some of the fundamental processes operating in thrust systems, such as out-of-sequence thrusting, timing of fault reactivation, and the length-scale of the ramp thrusts in foreland basins. Preliminary results indicate that hinterland-verging thrust faults that are located far from the hinterland may be active prior to faults with similar orientations that are close to the hinterland. Analytical and numerical results are currently being evaluated.