Deep structure of Japan subduction zone as derived from local, regional, and teleseismic events

In the crust and uppermost mantle, low-velocity zones are clearly visible beneath active volcanoes. In the mantle wedge the low-velocity zones generally parallel with the slab and exist continuously to a depth of about 200-km, which is consistent with the petrological, geochemical and geodynamic studies. The existence of volcanism-related low-velocity anomalies in the mantle wedge is a general seismological characteristic of subduction zones. The Pacific slab beneath Japan is imaged more clearly than in previous studies as a high-velocity zone with a thickness of 80-90 km and a P wave velocity 4-6% higher than the normal mantle. Lower velocity anomalies are found in the mantle below the slab. -from Authors