Figure 2. Parameter choices in the rupture scenarios: (a)
Depth-varying frictional property of (a – b ) on fault;L and d denote the apparent along-dip thickness of the
updip transition in velocity-dependence behavior and the apparent
along-dip thickness of the conditionally stable layer, respectively. The
transition from -0.0015 to -0.003 below d has the same (a– b ) gradient as L . (b) Depth profile of the effective
normal stress (\(\sigma\)). (c) Depth profile of the critical distance
(Dc ).
We assume that the effective normal stress \(\sigma\) to follows an
overburden pressure gradient at hydrostatic pore pressure condition from
the trench to 40-km along dip (~10 km depth). We also
set that \(\sigma\) has a minimum value of 5 MPa at the trench, such
that \(\sigma\) gradually increases to 50 MPa at 40-km downdip. Below
40-km downdip, \(\sigma\) is a constant of 50 MPa, assuming an
overpressured condition with lithostatic pore-pressure gradient (Rice,
1992) (Figure 2b).
We build two velocity structure models for our dynamic rupture models
(Figure 3). One is heterogeneous velocity structure with depth-varying
upper-plate P-wave velocity (Vp ), S-wave velocity
(Vs ), and density (\(\rho\)) reported by Sallers
& Ranero (2019) that are constrained by seismic surveys, and a
two-layer velocity structure for the footwall that captures the
first-order feature in the downgoing plate. Below 24 km depth in the
hanging wall, Vp , Vs , and\(\rho\) stay constant at 6.7 km/s, 3.9 km/s, and 2.9
g/cm3, respectively. The other is homogeneous velocity
structure with uniform Vp, Vs, and \(\rho\) in the entire model (both
the hanging and footwall) with values for those of rocks of the
overlying the megathrust at 24-40 km depth.