Dynamics of Large-Scale Strike-Slip Fault Formation: Microplate Capture During Subduction Termination

The thinning and destruction of cratons often accompany subduction processes, during which strike-slip faults may form. For instance, the northward propagation of the Tanlu Fault during the Mesozoic coincided with the thinning of the North China Craton. However, the mechanisms underlying the formation of intracontinental strike-slip faults remain poorly understood. In this study, we demonstrate how microplate capture by a subducting plate drives the transition from subduction to intracontinental strike-slip motion. Using 3D thermo-mechanical models that incorporate fluid migration, we find that the motion of an oceanic plate transitions from being accommodated at a mid-ocean ridge to the megathrust between the subducting slab and the overriding plate, and ultimately to an emergent, fluid-weakened intracontinental strike-slip fault. This transition occurs during slab detachment, triggered by decaying subduction convergence, the strengthening of the megathrust due to reduced water release, and eventual subduction termination. The extension of the overriding lithosphere facilitates the formation of the strike-slip fault. Our computations suggest that the connection between a low-viscosity, high-permeability subducted plate interface and the lower crust of the overriding plate promotes shearing, fluid transfer, and the eventual development of strike-slip faults.