Influence on Earthquake Distributions in Slabs from Bimaterial Shear Heating

People have proposed various mechanisms for understanding how deep focus earthquakes (DFEs) occur within deep-subducting slabs where the normal brittle failure is not a preferable regime. This chapter numerically investigates how shear heating from the bimaterial instability at the phase loop impacts the thermal structure of the subducting slab. It further discusses the dynamical implications for the lack of DFEs in the ASZ. The chapter suggests suggest that shear heating around the 410 km two-phase coexistence loop (i.e., olivine and spinel) may reduce the deviatoric stress level, and then can reduce the tendency toward transformational faulting. The phase loop makes it possible for a reduction in elastic modulus and consequently act as the bimaterial interface for providing intense shear heating within the loop. A localized zone with a low deviatoric stress level represents a new concept in subduction dynamics and may be able to explain the aseismic zone.