Figure 2
3D view of the model setup. (a) Material layout: a vertically layered overriding plate with upper crust, lower crust, and lithospheric mantle is underlain by a subducting plate with a cylindrical slab and a convex-upward-shaped indenter in the back and middle part of the model box, respectively. To emulate the asymmetric geometry of the southern Alaskan plate corner, the indenter bulge curves strongly towards the front part of the model, where the subducting slab is absent, in contrast to previous studies that assumed a symmetric model configuration15,16,17,24. The shape of the indenter is highlighted by gray isolines. The overriding and subducting plates are separated by a rheologically weak interface layer. To better illustrate the internal structure of the model, the plate interface is not shown in the lower part of the indenter. The S-line represents the intersection of the downgoing plate with the bottom of the model domain. (b) Velocity boundary conditions: the horizontal velocities applied to the left and right sides of the model box cause the overriding plate to move horizontally in the negative X-direction (red color), while the subducting plate moves in the opposite course (blue color). The inflow of lower plate material is mass-balanced by a vertical outflow through the bottom surface, which gradually increases from the left side of the model towards the S-line (see the downward component of the velocity vectors shown in shades of gray), corresponding to a rotational motion of the subducting slab. The resulting relative motion of the overriding and subducting plates along the transitional zone of the weak interface (gradual color transitions) includes convergence (corresponding to the Aleutian Megathrust subduction zone) and dextral transform (the strike-slip Fairweather fault) at the principal (X-perpendicular) and lateral (X-parallel) boundaries of the subducting plate, respectively. See “Methods” for more details on the model setup.
