3-D Discrete Element Modeling of Continental Fault System Evolution Under Oblique Boundary Conditions

Oblique displacement in continental tectonic setting often leads to complex fault systems that incorporate both dip-slip and strike-slip motion, with fault geometry and seismic activity developing across subsequent earthquake cycles. Understanding how boundary conditions influence fault growth, rupture dynamics, and off-fault deformation is an ongoing challenge in tectonics and earthquake physics. In this study, we are using three-dimensional discrete element models to analyze the evolution of continental fault systems under oblique boundary conditions.Specifically, we employ a numerical sandbox that represents the continental crust as a brittle layer where deformation can localize as a result of fracture nucleation, propagation and coalescence, without any a priori assumptions on its spatio-temporal evolution. Transtensional and transpressional loadings are applied through combined normal and shear components of deformation. Our simulations show cyclic stick-slip behavior, defined by periods of elastic responses followed by fault ruptures. Thanks to the model’s capability, we analyze the evolution of the emerging fault geometry, the ruptures extent, as well as slip partitioning throughout the simulated earthquake cycles. Particular emphasis is placed on the spatial distribution of damage, the development of fault-related topography on the surface, and the role of obliquity in controlling rupture propagation. Our findings show strong relationships between imposed boundary conditions, fault system configuration, and seismic rupture characteristics.