Three-Dimensional Particle Dynamics Simulations of Oblique Plate Convergence

Many convergent boundaries around the world exhibit significant curvature (e.g., Himalayas, Caribbean Arc, Aleutian arc), resulting in spatially varying convergence directions. The along-strike transitions from normal convergence to oblique convergence can produce a range of deformation structures reflecting the degree of strain partitioning along the boundary, including strike-parallel extension and strike-slip faulting. To explore the geometry and controls on these structures in more detail, and to better resolve the stresses and strains responsible for such deformation, we have carried out three-dimensional particle dynamics simulations using the discrete element method (DEM). Simulations are carried out in a numerical sandbox scaled to 20 km wide by 60 km long. A curved vertical wall of particles defines the backstop, which emerges through a fixed planar wall of particles into a layer of particles sedimented under gravity. Using visualization tools provided by Generic Mapping Tools (GMT) and Earth Vision (EV), we extract and display specific particle properties and assemblage attributes to fully interpret and analyze the deformation history and stress evolution. At first order, imbricate thrust faulting is observed at the head of the backstop, whereas distinct strike-slip faulting occurs along the lateral margins. As expected, the oblique convergent zones exhibit more complicated deformation, including extensional faults and offsets. The emergent structures are compared with analogous global plate boundaries to better understand the controls on deformation styles in these settings.