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

在南纬44 ~ 49、西经74 ~ 71的范围内进行了地震观测。60个地震仪在该地区安装了两年。我们使用地震层析成像，面波分析和接收函数分析的方法。用P波和S波进行的地震层析成像研究揭示了该地区的地震结构。地震构造沿纬度沿着由北向南变化。研究区北方板块俯冲，倾角10-20 °。在这个区域，旧的板块下降到另一个板块之下。在该区东部，板块倾角急剧增大。俯冲板片倾角横向变化大，在俯冲板片倾角陡的地区，俯冲板片倾角约为30 ~ 45 °。在宽区域观察到的板坯弯曲。洋脊俯冲的区域显示出特征性的构造。低速区被检测到低于板坯。洋脊俯冲区也具有低速特征。研究结果表明，该地区的地幔速度比正常地幔速度低10%，热地幔向上隆起至较浅部位。考虑热结构的岩石学研究揭示了俯冲带的精细图像，即高温脊是下降区。

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.