Flat Slab Driven Upper Plate Deformation

A big interest of mine is how the subducting plate drives deformation in the overriding plate. In regions of flat slab subduction, the slab couples strongly to the base of the upper plate and transfers stress to the upper plate. This can cause far-field mountain building and can drive motion of the upper plate along the path of subduction.

In south-central Alaska, our high-resolution, geographically referenced, 3D numerical models, which use the modern slab geometry (slab model SlabE115) and include a large intracontinental shear zone, the Denali fault, show that the flat slab drives northwest motion and counterclockwise rotation of the upper sliver plate, the Wrangell block. Our models show that a weak fault (10^17 Pa s) and a highly coupled interplate shear zone (10^21 Pa s) produce the fastest sliver velocities. This model is a good fit to the direction of observed GPS motion and contributes up to 20% to observed long-term Denali fault slip rates. For more information see some figures below and check out my 2017 Tectonics paper!