南海西北部与红河地区地球物理场及其地壳深部结构特征

CHARACTERS OF GEOPHYSICAL FIELDS AND DEEP CRUSTAL STRUCTURES OF NORTHWESTERN SOUTH CHINA SEA AND HONGHE REGION

分析了南海西北部与红河地区地球物理场特征 ,计算了研究区重、磁资料的一阶小波细节变换、四阶小波逼近变换。根据重力场资料以及南海北部盆地钻井取样的测试结果 ,同时参考在研究区进行的地震勘探结果 ,对研究区的地壳结构进行了反演计算。结果表明 ,研究区域地壳结构较为复杂 ,地壳厚度在 1 7— 38km之间 ,总的趋势由陆向洋地壳厚度逐渐减薄 ,反映出该区域地壳具有陆壳、过渡壳的性质 ,同时存在上地幔隆起区及凹陷区。用地震层析成像结果与重力资料计算出的地壳分布趋势进行了对比验证。根据地幔对流结果探讨了研究区深部地球动力学特征及其与深部地壳结构的关系。

This paper analyzed characters of geophysical fields in the northwestern South China Sea and Honghe region. One-step detail and four-step approach wavelet transforms of gravity and magnetic anomalies of the study area were calculated. Crustal structure of the study area was retrieved based on gravity data, testing results of core logging in the northern basins of South China Sea, and seismic probing results of the study area. The results show that the crustal structure of the study area is complex, with the Moho depth from 17 to 38km; the crustal thickness decreases from land to ocean, indicating that the crust has the characters of continental crust and transitional crust. The result obtained from seismic tomographic imaging was used to contrast and validate the result from gravity data. The relationship between deep crustal structure and geodynamical features of study area was discussed on the basis of mantle convection results.