利用接收函数反演青藏高原西部地壳S波速度结构  

Crustal shear-wave velocity structure beneath the western Tibetan plateau revealed by receiver function inversions

作　　者：武振波[1,2] 徐涛[1,3] 武澄泷 张明辉[1,2] 田小波[1,3] 滕吉文[1] 

机构地区：[1]中国科学院地质与地球物理研究所岩石圈演化国家重点实验室,北京100029 [2]中国科学院大学,北京100049 [3]中国科学院青藏高原地球科学卓越创新中心,北京100101

出　　处：《地球物理学报》2016年第2期516-527,共12页Chinese Journal of Geophysics

基　　金：中国科学院战略性先导科技专项(XDB03010700);中国地震局公益性行业科研专项(201408023);国家自然科学基金(41174075;41274070;41374062;41474068)联合资助

摘　　要：相对于宽阔的腹地,青藏高原西部南北向宽度仅约600km,却记录了印度和欧亚板块汇聚的深部过程及其响应.本文用22台宽频带流动地震台站在西缘构建了一条南北向探测剖面（～80°E,TW-80试验）.利用接收函数反演剖面下方S波速度结构,综合西部已有的宽频带探测结果,分析认为：印度板块向北俯冲可能已到达班公湖—怒江缝合带附近,俯冲过程中下地壳发生榴辉岩化;喀拉昆仑断裂带、班公湖—怒江缝合带、阿尔金断裂带均为切穿地壳的深断裂,莫霍面发生错断;喀拉昆仑断裂带和龙木错断裂带之间的中上地壳没有发现连续的S波低速体,说明可能缺乏解耦层,支持青藏高原西部地壳为整体缩短增厚模式.The collision of Indian and Eurasian plates is the most significant geological event on the Earth since Cenozoic era.How the subduction of the Indian plates occurs under the Tibetan plateau is one of the topics receiving much attention.Whether the boundaries between inner micro-blocks of the Tibetan plateau cut through the crust is another focused issue,which is of great significance for the deformation mechanism of the Tibetan plateau.To help address these issues,we performed a passive-source seismic survey profiling through the western Tibetan plateau.The receiver function method was used to study the crustal shear-wave velocity structure along the survey line.Firstly,we selected the similar receiver functions for each station bydiscarding the weird waves,then stacked the rest of results to obtain waves of high signal-tonoise ratio.Secondly,the inversion was operated with the Neighborhood algorithm.The Neighborhood algorithm made use of the geometrical constructs known as Voronoi cells to derive the search in the parameter space.It is known that this algorithm produces a selfadaptive search behavior.The inversion results of all stations are shown as a 2Dimage.As we expected,the shear-wave velocity structure along the survey line coincides with the migration of common conversion point（CCP）of the receiver functions.The earthquake of MS4.0 mainly happened beneath the Karakorum fault zone and the Longmu Co fault zone,which are featured by low shear-wave velocity in the upper-middle crust at both ends of the profile.The subduction of Indian plate under the Tibetan plateau probably reaches the BangongNujiang suture based on the comprehensive analysis in this study and the previous work on the western Tibetan plateau.The Karakorum fault zone,Bangong-Nujiang suture and the AltynTagh fault zone cut through the whole crust leading to the Moho offset.The absence of low shear-wave velocity in the upper-middle crust between the Karakorum fault zone and the Longmu Co fault zone probably indicates the lack of the decoupli

关 键 词：青藏高原 接收函数 S波速度结构 印度板块 莫霍面 

分 类 号：P315[天文地球—地震学]