南海中北部OBS2006-3地震剖面中横波的识别与应用  

Identification and application of shear waves along the profile OBS2006-3 in the mid-northern South China Sea

作　　者：卫小冬[1,3] 赵明辉[1] 阮爱国 丘学林[1] 夏少红[1] 朱俊江[1] 黄海波[1,3] 

机构地区：[1]中国科学院边缘海地质重点实验室,南海海洋研究所,广东广州510301 [2]国家海洋局第二海洋研究所,浙江杭州310012 [3]中国科学院研究生院,北京100049

出　　处：《热带海洋学报》2010年第5期72-80,共9页Journal of Tropical Oceanography

基　　金：科技部“973”项目(2007CB411701);国家自然科学基金(40876035;40776025);中国科学院南海海洋研究所领域前沿项目(LYQY200704);中国科学院知识创新工程(KZCX2-YW-Q05-04);广东省自然科学基金(07004190)

摘　　要：纵横波联合探测可以获得丰富的地下结构信息。纵横波速比和岩石泊松比在预测岩石圈的岩性、物性等介质属性方面有重要的作用。通过对比南海中北部OBS2006-3地震剖面垂直分量和径向分量上的纵横波走时、视速度以及质点运动轨迹,识别出了转换横波震相。本文以OBS8和OBS10台站的数据为例,说明了横波识别的方法,并在拟合好的P波速度模型基础上,利用RayInvr软件对转换横波震相进行了射线追踪,确认了PwSs3、PgSs3、PmS等几组转换震相,计算了这两个站位下的波速比和泊松比。根据OBS2006-3测线下地壳高速层的P波速度(VP=7.20—7.25km·s-1)、S波速度(VS=4.20—4.23km·s-1)、泊松比(0.24)等参数,初步推断下地壳高速层是由上地幔岩浆底侵作用形成。Applying the joint exploration of P-wave and S-wave,the complex subsurface crustal structure can be obtained.The association of P-wave velocity and S-wave velocity is very sensitive to the physical state of rocks,and is thus very useful in lithological studies.Compared with travel-time of P-wave and S-wave,apparent velocity and particle＇s moving trajectory in vertical-component and radical-component seismic sections,converted S-wave phases were identified in OBS8 and OBS10 along the profile OBS2006-3 in the mid-northern South China Sea.In this paper,taking these two OBSs as examples,we discussed identification and analysis of converted S-waves in detail.A few of S-wave seismic phases（e.g.,PwSs3,PgSs3,PmS） were identified based on the optimum P-wave model using the software Rayinvr and the ratio of Vp/Vs and Poisson＇s ratio are calculated beneath these two OBSs stations.Based on P-wave velocity（VP=7.20-7.25km·s-1）,S-wave velocity（VS= 4.20-4.23km·s-1） and Poisson＇s ratio（0.24）,we suggest that the high velocity layer in the lower crust has a mafic composition that may originate from magmatic underplating.

关 键 词：海底地震仪(OBS) 转换横波 纵横波速比 南海中北部 

分 类 号：P738[天文地球—海洋地质]