Figure 2. Parameter choices in the rupture scenarios: (a) Depth-varying frictional property of (ab ) 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 (ab ) 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.