南海中北部陆缘横波速度结构及其构造意义  

Crustal structure of shear waves and its tectonic significance in the mid-northern continental margin of the South China Sea

作　　者：卫小冬[1,2,4] 赵明辉[1] 阮爱国 丘学林[1] 郝天珧[3] 吴振利[2] 敖威[1,4] 熊厚[1,4] 

机构地区：[1]中国科学院边缘海地质重点实验室,中国科学院南海海洋研究所,广州510301 [2]国家海洋局第二海洋研究所,杭州310012 [3]中国科学院地质与地球物理研究所,北京100029 [4]中国科学院研究生院,北京100049

出　　处：《地球物理学报》2011年第12期3150-3160,共11页Chinese Journal of Geophysics

基　　金：国家重点基础研究发展计划(973计划)(2007CB411701);国家自然科学基金项目(40876035,41074058,40776025,91028002)资助

摘　　要：纵横波联合勘探可以得到更多关于岩石圈层岩性、物性等介质属性方面的信息,有效提高地壳物质组成的约束性.在纵波速度结构模型的基础上,通过射线追踪和走时拟合对OBS2006-3地震剖面径向分量的转换震相进行了横波速度结构模拟.结果表明:沉积层1、沉积层2的横波速度分别为0.7～0.9 km/s和1.6～1.7 km/s,波速比由2.64～3.16变化到2.41左右,较高的波速比表明沉积层固结程度不高;中生代沉积层横波速度由浅部的2.6 km/s增大到3.0 km/s,波速比为1.74～1.80;地壳中波速比为1.74～1.82,表明该剖面地壳为陆壳性质;下地壳高速层的横波速度为4.0～4.2 km/s,纵横波速比为1.73～1.78,揭示高速层的物质组成为铁镁质的基性岩,推断其与海底扩张停止之后的岩浆底侵作用有关.The joint exploration of P-wave and S-wave can obtain amount of information on lithology and geophysical properties, which effectively improve the composition constraint of the deep crustal structure. Based on the optimum P-wave model, the shear waves recorded on the radial components of profile OBS2006-3 have been modeled by 2-D ray-tracing. The S-wave velocities in sedimentary layer 1 and sedimentary layer 2 are of 0. 7-0. 9 km/s and 1.6-1.7 km/s, respectively. TheVp/V- ratios in these sediments vary from 2.64-3.16 to 2.41. The relatively high Vp/V- ratios are probably related to unconsolidated sediments. In the Mesozoic sedimentary layer, the S-wave velocity increases gradually from 2. 6 km/s at the top to 3. 0 km/s at the bottom, and the Vp/V- ratio is of 1. 74-1.80. The V-,/V- ratio of 1. 74-1.82 in the crust is considered to be the continental crust. The S-wave velocity and Vp/V- are 4.0-4.2 km/s and 1.73-1.78 of the High Velocity I.ayer （HVI.） in the lower crust, which suggest that the HVI. has a mafic composition that may originate from underplating of the igneous rocks after the cessation of the seafloor spreading.

关 键 词：海底地震仪 转换横波 波速比 下地壳高速层 

分 类 号：P315[天文地球—地震学] P542[天文地球—固体地球物理学]