【摘要】 本文利用中、美联合调查南海海洋地质项目所采集的双船地震扩展排列剖面资料，研究了南海北部陆缘的地壳结构．其特征为：从陆架到深海平原，地壳呈阶梯状减薄，地壳厚度分别为２６—２８ｋｍ，２３—２４ｋｍ，１３—１５ｋｍ，以及南海洋盆中５—７ｋｍ厚的洋壳，反映了地壳在新生代早期是幕式拉张的．地壳底部存在高速地壳层，地震波速度为７．１—７．４ｋｍ／ｓ．它是在地壳被拉张后，上地幔熔融物质上涌到地壳底部冷却而形成的．更多还原

【Abstract】 North continental margin of South China Sea was passive in Cenozoic which developed 60 Ma B.P.The margin is a ideal one in the world for study of tectonic evolution of passive continental margin.The crustal structure is studied by using the data of two-ship seismic extended spread profiles acquired in project"USA-China Joint Investigation on Marine Geology of South Chine Sea". The crustal structure is featured by four-terrace thinned crust from continental shelf to deep sea plain. Crust thicknesses of the four terraces are 26-28 km,23-24km,13-15km and 5-7 km (oceanic crust)in South Chins Sea basin. This shows that it was episodic extensional in early Cenozoic. High-velocity layer with seismic velocity of 7.1-7.4 km/s is found on the bottom of the crust. The layer was brought about by the process that melted materals from upper mantle cooled on the bottom of the crust after extension of the crust.更多还原