Subduction initiation along the inherited weakness zone at the edge of a slab: Insights from numerical models

A preexisting weakness zone in the lithosphere is required to initiate subduction. Here, we focus on a new type of weakness zone, a Subduction-Transform Edge Propagator (STEP) fault, which is inherited from a tear along the edge of a slab. Using coupled thermal–mechanical models, we show that STEP fault-perpendicular convergence results in a dipping shear zone in any tectonic setting. At a continental margin, this shear zone dips towards the...