Relating Slip Behavior to Off-Fault Deformation Using Physical Models

Deformation in transform systems is accommodated by discrete fault slip and distributed off-fault deformation. Here, we consider how a change in slip behavior along a fault can influence the distribution between on- and off-fault deformation. We use a physical experiment to simplify the geometry, material properties, boundary conditions, and slip history along a strike-slip fault to directly observe patterns of off-fault deformation. We document deformation of a silicone slab on a simple shear apparatus using particle image velocimetry (2D) and photogrammetry (3D). The experimental results show regions of topographic highs and lows on either side of the slip transition that grow, evolve, and are displaced with progressive strain. The experimental dilatation field shares similarities with strain fields in central California along the San Andreas fault, which suggests that a change in slip behavior may explain some of the real-world patterns in short- and long-term deformation.