MEASURING THE EVOLUTION OF FAULTS AT RESTRAINING BENDS IN CLAYBOX EXPERIMENTS

How do faults evolve at tectonic plate boundaries? Rather than waiting 1 million years to see how faults evolve, we can compress the time of fault development to several hours with scaled tabletop experiments using wet kaolin. Upon deformation, the bi-viscous wet kaolin produces both localized faulting and distributed shear that simulates crustal material. The goals of my thesis research are 1) to investigate the strike slip fault evolution around a restraining bend with variable kink angle and step over distance and 2) to validate new Particle Integrated Velocimetry (PIV) techniques. Changing stepover distance and kink angle of the restraining bend alters the degree of secondary faulting as well as the amount of uplift within the bend. The pattern of active faulting shifts during the experiments with fault abandonment, new fault growth and some fault reactivation. We use two techniques to measure the dip and strike slip along each fault and to determine the proportion of slip to distributed deformation in each experiment. The traditional technique uses offset markers. These markers are recorded using 3D laser scans, which show both fault parallel displacement of the markers and uplift but require stopping of the experiment. The new PIV software tracks surface particles in a series of photos to show the full two-dimensional displacement field without pausing the experiment. We compare the accuracy and ease of use of the two techniques. Also we re-ran some experiments to ensure repeatability of each scenario. The fault evolution observed in the claybox can guide predictions of fault development in active tectonic regions and may assist in seismic hazard estimates. By comparing our results to real-world restraining bends, we can better understand the role of the bend geometry in the development of secondary features around restraining bends on earth.