Super-deep seismic reflection study in growth of continental crust beneath the Hidaka Collision Zone, Hokkaido

为了探测在中下地壳拆离的下降千岛岛弧与俯冲太平洋板块上表面之间的三维几何关系，在日高碰撞带南部的低噪声区Samani镇进行了超深日高2000地震反射实验。这次实验的目标位于50公里深。地震测线设置在两个方向上，NW-SE（平行于太平洋板块俯冲）和NE-SW（接近千岛岛弧碰撞）。线路总长度达到32公里。主要规格如下：以约300米的间隔发射，5个振动器平均扫描30次（6-30 Hz，24秒），以50米的间隔9个拾取/接收点。基本处理产生了相当好的剖面，成功地显示了HMT（日高主逆冲断层）的较深部分和俯冲的太平洋板块。千岛弧下降的图像仍然不清楚。进一步的处理将改善现有的剖面，并提供关于下降的千岛弧和俯冲的太平洋板块之间的几何关系的新的强有力的数据。

In order to detect the 3-D geometrical relationship between the descending Kuril arc delaminated at the middle lower crust and the upper surface of subducting Pacific plate, the super-deep seismic reflection experiment, Super-Deep Hidaka 2000, was conducted in the low noise-level area, Samani Town, southern part of the Hidaka Collision Zone. The target of this experiment is located down to 50 km deep. Seismic lines were set up in two directions, NW-SE (parallel to the Pacific plate subduction) and NE-SW (neally paralle to the Kuril arc collision). Total length of the lines reached 32 km long. Main specifications were as follows : Shot at about 300 m interval with 30 Sweeps in average(6-30 Hz, 24 sec) by 5 vibrators, 9 pick-ups / receiving point at 50 m interval. The basic processing produces fairly excellent profiles which is successful in exhibiting both the deeper part of the HMT (Hidaka Main Thrust) and the subducting Pacific plate. The image of descending Kuril arc is still unclear. Further processing will improve the present profiles and provide the new powerful data on the geometrical relationship between the descending Kuril arc and the subducting Pacific plate.