• intermediate-depth earthquakes;
  • slab dehydration;
  • slab weakening;
  • fluid flow

When subducting oceanic plates descend into the Earth's mantle, they bring a significant amount of water with them that is subsequently released at depths.Faccenda et al. used a thermomechanical model of a subducting dehydrating oceanic plate to study fluid flow in the dehydrating slab. They show that as a slab bends and unbends as it descends, stresses drive fluids toward a layer of lower pressure in the center of the plate. Together with the dehydrating oceanic crust, this fluid-rich layer forms a double hydrated zone, which the authors believe corresponds to 20- to 30-kilometer-thick regions called double seismic zones that have been observed in seismological studies.