BREAKING THE OCEANIC LITHOSPHERE OF A SUBDUCTING SLAB: THE 2013 MW7.7 KHASH, IRAN EARTHQUAKE
Finite-fault slip models derived independently from each data source exhibit similar spatial rupture characteristics and require a rupture width of at least 50km, with the majority of slip occurring in the subducted oceanic mantle. These models, along with the hypocentral depth, suggest that at least half of the subducted lithosphere, including the mantle and entire crust, ruptured during the earthquake - confirming with high resolution that this earthquake nucleated from a neutral plane and ruptured the portion of the slab undergoing extension. Both data sets are best-fit by the north-dipping focal plane oriented at an oblique angle to the trench. Combining our earthquake slip distributions with the causative fault orientation and geometry of the local subduction zone, we assess the potential activity of several mechanisms for the generation of mantle and intermediate depth earthquakes. We hypothesize that the Khash earthquake likely occurred as the combined result of slab bending stresses acting on a preexisting fault that formed prior to subduction and that was weakened by dehydration of hydrous minerals.