NUMERICAL ANALYSIS OF FAULT EVOLUTION OF RESTRAINING BENDS

The work minimization hypothesis holds that the fault networks propagate new faults to reduce the total work that must be done on the system to facilitate slip. Claybox analog experiments explored the effect of the restraining bend geometry on fault evolution. A fault with a predetermined restraining bend shape is cut into the wet koalin. Some kink configurations produced complex fault networks with uplift, but a few configurations only slipped on the main fault and no significant secondary structures were produced. However, work cannot be analyzed from direct observation of analog models, so numerical models of the claybox experiments are required.

The numerical models simulate the claybox deformation by applying representative boundary conditions, wet koalin viscosity and wet kaolin density. The secondary faults, if present, start their development at 30 mm displacement. Simulate the evolution of faulting observed in the claybox experiments by adding the faults to sequential numerical models. The work required to deform the system can be calculated from both the stresses on the boundaries of the model and the internal strain energy within the model. The evolution of work with model-simulated fault growth can show whether the faults in the claybox evolve to minimize work of the system.

As an additional test of fault evolution, we investigate the early stage of fault growth and permit fault development via Drucker-Prager yielding. Comparison of Drucker-Prager predicted fault patterns and claybox observations will reveal if the faults in wet kaolin propagate via this mechanism. The work required for deformation along the Drucker-Prager predicted faults will be compared to the work of along faults observed in the claybox..