黄海深部结构与中朝—扬子块体结合带在海区位置的地球物理研究

Deep structure and boundary belt position betweenSino-Korean and Yangtze blocks in Yellow Sea

以黄海及其邻区为研究对象 ( 32～ 4 2°N ,1 2 0～ 1 30°E) ,以研究区的空间重力异常、布格重力异常和地震层析成像数据为基础 ,在研究区中分辨出方向各异的主要断裂带并给出它们的分布。对在朝鲜半岛存在的一条近SN向分布的断裂带进行了重点讨论。根据重力数据、莫霍深度分布特点和层析成像的结果 ,认为该断裂带的两侧应属于不同的构造地质单元 ;提出该断裂带与五莲—青岛断裂带和济州岛南缘断裂带一起组成了中朝与扬子块体在黄海海区的边界结合带的认识 ;并推测在三叠纪的晚期 ,沿郯庐断裂带和该断裂带曾分别发生过左旋和右旋走滑。受SN向挤压应力的作用 ,(下 )扬子块体被平移嵌入到中朝块体之中。因此 ,两个块体在海区的结合带为一个巨大的“Z”

Free-air and Bouguegravity anomalies and seismic tomography show major faults in the Yellow Sea and adjacent areas between 120°E and 132°E, 32°N and 42°N. It is inferred from the geophysical data in the study area that a fracture along SN direction near the west margin of Korean Peninsula can be a part of boundary between Sino-Korean and Yangtze blocks. The whole boundary in Yellow Sea is consisted of Wulian-Qingdao Fault, South Marginal Fault of Jeju Island and the West Margin Fault of Korean Peninsula. It is inferred that during late Triassic period the compression stress in SN direction facilitated the northward movement of Yangtze block, leading to sinistral slip along Tancheng-Lujiang fault zone in Eastern China and dextral strike slip along the West Marginal Fault of Korean Peninsula. The movement resulted in the insertion of the Yangtze block to the Sino-Korean block. So the boundary belt between the two blocks in Yellow Sea presents a giant Z-shaped pattern.