Research of deep structure and phenomena at the Chilean ridge subduction region

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We deployed seismic observation at the area with the latitude of 44 S-49 S and longitude of 74W-71W. The 60 seismometers were set up at the area for two years. We use the methods of seismic tomography, surface wave analysis, and receiver function analysis. Seismic tomographic studies with P- and S- waves revealed the seismic structure at the area. The seismic structure changes from north to south along the latitude. In the northern part of the research area, the slab is subducting with dip angles of 10-20 deg. In this area, the old plate is descending beneath the other plate. At the eastern part of the area, the dip angle of the slab increase sharply. The large lateral variation of the dip angles of the subducting slab was found. At the area with steep dip angle of the slab, the dip angle of the slab is estimated to be 30 - 45 deg. The bend of the slab observed at the wide area. The region that the ridge is subducting shows a characteristic structure. The low velocity zone was detected below the slab. The ridge subducting area is also characterized to be low velocity. The velocity of the area was estimated to be 10 % lower than normal mantle velocity It is considered that the hot mantle rise up to the shallower part.The petrology studies considering thermal structure reveal a fine image of the subduction zone that the high temperature ridge is descending region.