Subduction occurs along a fault, along which a hanging wall, or overriding slab is thrust over an overridden slab, also called the subducting slab. The fault that acts as the subduction interface is at the bottom of the Apennine wedge, characterized by a deep groove in the surface, typically filled with sediment, as sedimentation here occurs at a much faster rate than subduction. In north Italy the dip of this interface is 30° to 40° at a depth of 80–90 km.