Crust Deformation around Non-Planar Transform Faults: Observation and Physical Modeling

Crust deformation around non-planar transform faults is manifested by numbers of folds and secondary faults surrounding the transform faults. The distribution and spatial extent of folds and secondary faults may differ along individual transform faults. To better understand the mechanisms controlling the deformation around transform faults, we use a physical model to simulate fault slip and crust deformation along a conceptual transform fault with a restraining bend. With the model, we explore the effects of several key parameters, including viscosity in lower crust and upper mantle, fault frictional coefficient, aspect ratio of fault bend, and relative plate velocity. The model results show that restraining bends tend to impede fault slip, increase shear stress in the surrounding crust, and localize strain in a pair of belts off the fault zone. These effects are enhanced by high viscosity in the lower crust and upper mantle, high aspect ratio of bend width over fault length, fast relative motion of fault blocks, and high fault friction. These model results may help explain the diffuse deformation surrounding the Big Bend of the San Andreas Fault, and the more confined deformation around the Lebanon Bend of the Dead Sea Fault.