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.
Pre-earthquake Loading Stage
To simulate the interseismic (preconditioning) period, 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, the 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.