Evolution of fault efficiency at restraining bends within wet kaolin analog experiments

Restraining bends are regions of mechanical inefficiency along strike-slip faults where faults evolve to improve efficiency. Analog experiments using wet kaolin examine the evolution of a variety of restraining bends. Restraining bends with 15° bends continue to slip while systems with greater bends develop new faults. The new faults, which flank the uplifted region, accommodate right-lateral slip when parallel to the plate movement and oblique-slip motion when parallel to the restraining segment. Within the wet kaolin, strain is partitioned into fault slip and off-fault deformation, such as distributed shear and uplift. The wet kaolin produces restraining bend deformation patterns, fault sequence and mechanical efficiency similar to dry sand experiments and natural restraining bends. The propagation of new faults in the wet kaolin improves the mechanical efficiency of the fault system by increasing the ratio of fault slip to off-fault deformation. Local inefficiencies, such as linkage of faults via a sharp kink, do not affect the overall increase in efficiency of the linked fault system. Furthermore, wider restraining bend stepovers have lower mechanical efficiency than close stepovers, but the difference in mechanical efficiency decreases as faults grow and link up around the restraining bends. This study demonstrates that restraining bend fault systems evolve toward greater mechanical efficiency.