Text S2. Simulation Workflow

We seek to simulate the dynamic Coulomb Wedge model earthquake cycle (Wang and Hu, 2006) in our simulations. We first prepare the fault for dynamic slip by preconditioning it during steady backwall displacement, holding the initial basal friction at 0.04. This represents the interseismic stage. This preconditioning ensures high shear stress along the fault and the accumulation of elastic strain energy within the wedge. To simulate the dynamic stage of the earthquake cycle, we reduce the friction coefficient along the basal decollement beneath the inner wedge to approximate velocity weakening and either increase or maintain the basal friction beneath the outer wedge to approximate velocity strengthening. the internal friction coefficient is maintained at 0.30 for both the inner and outer wedges.
During the pre-earthquake loading stage, the right wall of the wedge moves inward at a constant horizontal velocity (vx) of 1 m/s, under constant basal friction conditions. During this preconditioning stage, the system state is recorded at increments of 200 m of backwall displacement. The internal stresses within the wedge are supported by elastic deformation at interparticle contacts, defining the potential energy of the system. During this stage, the wedge deforms, either extending or contracting, depending on the basal friction conditions and the predefined wedge geometry. The preconditioning stage is complete when the model reaches its steady state, State 1. Details about the implementation of preconditioning and the discussion about the steady state can be found in Wang and Morgan (2019).
Once the wedge reaches State 1, we simulate the second stage of dynamic earthquake unloading, culminating in the final State 2. At the start of the second stage, backwall displacement is stopped. Earthquake unloading is initiated by the reduction in basal friction beneath the inner wedge, and concurrent increase in friction beneath the outer wedge as appropriate.
For each model, a splay fault with a dip, varying from landward to seaward dipping is prescribed just before the earthquake unloading. A model without any prescribed splay fault is also constructed as a reference.
Table S1 Basal Friction Conditions along Megathrust and Splay Fault before and after Earthquake Unloading.