冲绳海槽南部基底构造特征

利用最新的重磁数据对冲绳海槽南部的基底构造进行了推断解释，研究表明，在冲绳海槽南部，莫霍面构造为一南北两端高，中间低的鞍状构造，地壳厚度在15.5~21 km之间变化.基底深度一般在4~6 km之间变化，表现为南段深度大，北段深度小，在北西向断裂系的作用下，基底局部构造大都成北西向展布，说明冲绳海槽早期的北东向带状构造受到了后期的北西向构造活动的强烈改造作用.在冲绳海槽南部发育有两条沿北北东向展布的火成岩带，一条分布在冲绳海槽扩张轴以东及琉球岛弧西侧下坡；另一条分布在冲绳海槽与琉球岛弧隆褶带的结合部位，火成岩主要是由北东向构造活动产生的，而与北西向断裂关系不密切.

The basement tectonics in south of the Okinawa trough

Based on the latest gravity and magnetic data the basement tectonics in south of the Okinawa Trough was deduced. The results show that Moho likes a saddle structure in south of the Okinawa Trough which is higher in the south and the north but lower in the middle, and the thickness of lithoshere changes from 15.5 km to 21 km. Popularly the basement depth changes among 4 km-6 km, and the depth is larger in south than in the north. Because the effect of NW faults, most the Tertiary local structures trend NW, which indicates that the early NE tectonic belts have been changed by the action of the faults trending NW. There are two igneous rock zones trending NNE in south of Okinawa Trough. One spreads in the east of spreading axis of Okinawa Trough and the west of downgrade of Ryukyu Arc. And the other one spreads in the integrated part of Okinawa Trough and the folded belt of Ryukyu Arc. The igneous rock might be mainly brought about by the action of NE faults,and had little effection by NW faults.