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文章利用天然地震的PS转换波研究了北部湾陆缘地区的地壳结构特征。PS转换波测量表明 :本区地壳内部存在 4个明显的转换界面 :PSC、PSG、PSM、PSM1,分别代表上地壳、中地壳底界以及Moho面 (下地壳底界 )和上地幔顶部的第一转换面。计算结果表明 ,本区上地壳厚约 12km ,中地壳厚约 9km ,下地壳厚约 11km ,Moho面深约 32km。地壳厚度 (或Moho面深度 )由海向陆变厚 (或变深 ) ,由内陆的灵山到海陆交界处的北海、合浦 ,Moho面深度 (或地壳厚度 )由 34km变为 30km左右。PS转换波测深结果还表明 ,本区内NE向钦防—灵山断裂、合浦—博白断裂以及NW向小董—合浦断裂向深部延至中地壳 ,属壳断裂性质。北部湾陆缘地壳性质上仍为陆壳 ,由陆向洋明显减薄 ,北部湾盆地发育于这一减薄陆壳的前缘 ,是由地壳进一步伸展减薄所形成的。
In this paper, the characteristics of crustal structure in the Beibu Gulf continental margin are studied by using PS seismic waves of natural earthquakes. PS conversion wave measurements show that there are four obvious transitional interfaces in the crust: PSC, PSG, PSM and PSM1, representing the upper crust, the middle crust bottom boundary, and the Moho surface (lower crust bottom boundary) A conversion surface. The calculation results show that the upper crust is about 12km thick, the middle crust is about 9km thick, the lower crust is about 11km thick, and the Moho surface is about 32km deep. The thickness of the crust (or depth of Moho) becomes thicker (or deeper) from sea to land. From the inland Lingshan to the Beihai and Hepu junctions at Hejian and Helu, the Moho depth (or crust thickness) changes from about 34km to about 30km. PS converted wave sounding results also show that NE to Qin defense - Lingshan fault, Hepu - Bobai fault and NW Xiao Dong - Hepu fault to the deep extending to the middle crust, the shell is a fault. The continental crust of the Beibu Gulf is still continental in nature and is obviously thinned from the ocean to the ocean. The Beibu Gulf basin developed at the front edge of this reduced continental crust is formed by the further extension and thinning of the crust.