THE FAULT LIFE-CYCLE: EVOLUTION OF STRAIN PARTITIONING WITHIN CLAYBOX EXPERIMENTS OF THE SOUTHERN SAN ANDREAS FAULT, CA

We simulate deformation along the southern San Andreas Fault within wet clay using a motorized device. The non-planar geometry of the present-day San Andreas and San Jacinto faults are cut into the clay using an electrified wire and a wooden template. Slip along the faults is driven by displacement of basal metal plates. Periodic laser scans provide a means to collect quantitative data from the experiments. Offset markers record slip rates and the 3D laser scans provide detailed uplift maps. The proportion of on-fault to off-fault deformation (e.g. slip to uplift) changes throughout the experiment as faults grow, shut-down and new faults develop. During first 20 mm of deformation, the faults show little slip and instead display shear zones. Between 20 mm and 40 mm of displacement, secondary faults initiate, localized slip develops along the faults, and broad uplift begins within the restraining bend. Between 40 and 60 mm of displacement, the restraining bend of the pre-cut fault shuts down. The evolution of faults within the wet clay experiments may mimic the life cycle of faults within the crust as faults initiate, grow and shutdown.