How far does a subduction wedge follow lubrication dynamics?

Applications of the lubrication dynamics in subduction zones generally assume very small wedge taper angles (α < 1°), satisfying the condition of flow within the subduction wedge sub-parallel to the bounding plates. However, many subduction systems have their plate interfaces with α far exceeding 1°. This article aims to address a fundamental question - is the lubrication theory valid for subduction wedges with α ≫ 1°? We test the validity by comparing its analytical solutions with the results obtained from the numerical solutions of full-form Stokes equations, and constrain α limit (<20°) in applying the lubrication theory with errors <5%. We also use this theory to evaluate the magnitude of dynamic pressure in subduction wedges as a function of subduction velocity, wedge geometry and its viscosity, and then demonstrate how such dynamic pressure eventually controls the overriding plate deformation and extrusion channel formation in convergent tectonics. Drops in dynamic pressure facilitate gravitational collapse of the overriding plate, which in turn initiates the extrusion channel in a wedge.