南海北部地球物理特征及地壳结构

为了研究南海地壳结构，中国和日本合作在南海北部首次进行了以炸药为震源的综合地球物理调查。经初步分析其地壳结构主要特征为：南海北部地壳分为沉积层、上地壳层、中地壳层及下地壳层。大陆架及上陆坡地壳厚度大、稳定。下陆坡地壳厚度除中地壳外，其他壳层厚度减薄且不稳定。深海盆地壳分３层，厚度虽薄但相对稳定，其底部缺失７．３ｋｍ·ｓ－１的高速层。测区内地壳总厚度：陆壳２６—３０ｋｍ，过渡壳１３—２２ｋｍ，洋壳为８ｋｍ。

GEOPHYSICAL CHARACTERISTICS AND CRUSTAL CONSTRUCTION IN THE NORTH OF SOUTH CHINA SEA

The preliminary analysis of integrated geophysical survey which was carried out in the north of South China Sea by joint research group of China and Japan is described in this paper. In order to further understand the crustal construction, the relationship of continental and oceanic crusts in the north of South China Sea, the seismic refraction survey was mainly carried out using dynamite as the source and OBS (Ocean Bottom Seismometer) as the receiving system for the first time in China. After data processing and preliminary analyzing, the main characteristics of the crustal construction are as follows. The crust in the north of South China Sea can be divided into sedimentary, upper,intermediate and lower crusts. The crustal thickness is large and stable in the area of continental shelf and upper slope and is decreased and unstable in the area of lower slope except the intermediate crust. The crust can be divided into three layers in the deep oceanic basin,of which the crustal thicknesses are relatively thinner than those in the continental shelf and slope area. The high velocity layer of 7. 3km. s-1 could not be observed below the oceanic crust. The following is the crustal thickness in different areas.The continental crustal thickness ranges from 26 to 30km. The transitional crustal thickness ranges from 13 to 22km. The oceanic crustal thickness is skin.