南海东南部陆缘地壳结构特征及其构造意义

南海东南部海域沉积厚度较大，礁体发育，构造演化复杂，导致深部结构探测不清楚，制约了对南部陆缘地壳结构的认识.本文通过对新采集和重新处理的多道地震剖面解释，结合钻井、拖网资料，对浅部地层和构造进行约束，同时利用附近海底地震（OBS）测线的速度结构，对深部结构和界面解释约束；在此基础上，开展了重震联合反演，分析地壳密度空间分布特征，结合重力梯度特征对构造单元进行识别.通过对东西两条测线的上下和全地壳厚度、拉伸因子比较，发现南海东南部的东西部深部结构存在差异性；礼乐断裂可能是礼乐和郑和地块的分界，并控制了两个地块在南海扩张时期的相对运动.

Characteristics of the crustal structure and its tectonic significance of the continental margin of SE South China Sea

The southeastern South China Sea has a large sedimentary thickness, a developed reef and a complex tectonic evolution, which leads to unclear detection of deep structures and restricts the understanding to the crustal structure of the southern continental margin. This paper interprets the newly acquired and reprocessed multichannel seismic profiles, combining with drilling and trawl data, constrains shallow formations and structures, and utilizing the seismic velocity structure of the nearby Ocean-Bottom Seismometer to constrain the deep structure and interface; on this basis, the gravity and seismic joint inversion is carried out to analyze the spatial distribution characteristics of crustal density, and the gravitational gradient features are used to identify the structural unit. By comparing the upper, lower and whole crustal thickness and the stretching factor of the two survey lines, it is found that there are differences in the deep structures of the east and west parts of the southeastern South China Sea; Liyue Fault may be the boundary between Liyue Block and Zhenghe Block, which controls the relative movement of these two blocks during the seafloor spreading stage of SCS.