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通过中美科学合作，在南海北部陆缘西部采集了一条地壳剖面，从阳江地区开始，经珠三坳陷、神弧－东沙隆起、西沙海槽至西沙－中沙台地．结果表明，珠三坳陷的地壳已减薄至２３ｋｍ，去掉新生代沉积，则只有１５ｋｍ厚．西沙海槽的地壳结构已具备裂谷特征，地壳强烈减薄，厚１４．４７ｋｍ；下地壳有高速地壳层，层速度为７．１ｋｍ／８，厚６．７ｋｍ．说明在新生代，南海北部陆缘西部受过强烈拉张，地壳减薄；上地幔部分熔融物质沿强烈拉张处侵入到地壳底部，使其地表形成裂谷．在西沙海槽的南部和北部，地壳结构差异很大，推测这里可能是由两个古老地块沿西沙海槽缝合起来，新生代早期的张性事件，又将这条古缝合线拉开，形成新生代裂谷──西沙海槽．
Through scientific cooperation between China and the United States, a crustal section was collected in the western part of the continental margin of the northern South China Sea. From the Yangjiang area, it passed through the Zhuansan depression, Shencao-Dongsha uplift, Xisha trough to Xisha-Zhongsha platform. The results show that the crust in the Zhujiang Depression has been reduced to 23 km and the Cenozoic sediments removed, only 15 km thick. The crustal structure of the Xisha Trough is characterized by rifting. The crust is strongly thinned with a thickness of 14.47 km. The lower crust has a high-speed crust with a velocity of 7.1 km / 8 and a thickness of 6.7 km. It shows that in the Cenozoic, the northern margin of the South China Sea experienced intense tension in the western margin of the South China Sea and the crust was thinned. Some of the molten material in the upper mantle infiltrated the bottom of the crust along the intense extension, causing the surface to form a rift. In the southern and northern Xisha troughs, the structure of the crust varies greatly. It is presumed here that there may be two ancient plots stitched together along the Xisha trough. In the early Cenozoic tensions, the ancient suture line was opened again. Formation of the Cenozoic rift ─ ─ Xisha trough.