Numerical simulations of mantle flow around slab edges

A simple kinematic-dynamic model of mantle flow around the slab-edge is constructed in order to understand the flow complexity there. The flow velocity on the top and the small boundary region around the shallow plate boundary is kinematically imposed in order to achieve a subduction-like feature and the flow in other part is dynamically calculated. The geometry of the plate mimics the region around the junction of Aleutian Islands and Kamchatka, that are examples of the convergent-transform fault plate boundaries. In a simple model in which the overlying plate is almost stationary, the lateral flow from the mantle under the subducting slab to the mantle under the neighboring plate is of minor importance, once the slab penetrates into the high viscosity layer where the downward flow encounters the resistance. Similar situation was found when the trench is advancing, that is, the trench moves toward the overlying plate. For the case with retreating trench, that is, the trench moves toward the subducting plate, a lateral flow exists even after the slab penetrates into the high viscosity layer, although its magnitude is significantly smaller than that of the plate velocity. The presence of a low viscosity layer just beneath the subducting plate may promote the emergence of lateral flow. A significant lateral flow is observed when the high temperature anomaly, that is, buoyant and low viscosity block carried by the movement of subducting plate, approaches the slab. These results may have important implications for the possible existence of trench parallel flow in the sub-slab mantle.