青藏高原东缘S波速度结构及其意义  

S-wave Velocity Structure of the Eastern Margin of the Tibetan Plateau

作　　者：江晓涛[1] 朱介寿[2] 王宇航[3] 杨正刚[1] 杜兴忠[1] 

机构地区：[1]中国水电顾问集团贵阳勘测设计研究院有限公司,贵州贵阳550002 [2]成都理工大学地球探测与信息技术教育部重点实验室,四川成都610059 [3]四川省地震局,四川成都610041

出　　处：《地震工程学报》2013年第4期885-892,共8页China Earthquake Engineering Journal

基　　金：国家自然科学基金资助项目(40839969;41074062)

摘　　要：利用从2009年到2013年在研究区域部署的50个流动观测台站及10个固定台站（中国数字地震台网CD-SN,四川地震台网）收集到的数据资料,采用接收函数线性反演的方法对研究区域的地壳上地幔S波速度结构进行研究,得出青藏高原东缘各台站的VS断面最显著的特征是速度很低,中地壳VS平均速度值为3.0～3.4km/s,上地幔VS速度值为4.0～ 4.5 km/s.地壳内普遍存在低速层,大部份低速层位于深度20～40 km的中地壳,在10～20 km的上地壳及40～60 km的下地壳中也出现少量的低速层.此外在青藏高原东缘南部地区也只有部份低速层出现.青藏高原东缘地壳流并不处处存在,而仅局限在有限区域,主要分布在中地壳内部（深20～40 km）.当地壳流遇到刚强的四川盆地地壳及上地幔阻挡时出现拆分现象,即产生向上或向下的2～3个分支,向上的一支引起上地壳隆升形成陡峻的山峰,向下的一支使莫霍界面下沉引起地壳增厚.To study the S-wave velocity （VS） structure of the middle and lower crust beneath the eastern margin of the Tibetan Plateau and viscous flow in the deep crust,we adopted data from a regional network of approximately 50 temporary broadband seismometers and 10 permanent seismic stations of the Chinese Digital Seismological Network （CDSN） to invert the detailed structure of the crust and the upper mantle in the eastern margin of the plateau and in Sichuan Basin by using the linear inversion method.We determined that from 0 km to 10 km,VS is lower in the basin because it contains a huge thickness of sediments characterized by low velocity.In contrast,the regions in the eastern margin of the plateau show a higher velocity.From 10 km to 40 km,the basin shows higher VS in the middle and lower crust.In contrast,the eastern margin of the plateau shows lower velocity; the average velocity of the middle crust is 3.0～3.4 km/s.From 50 km to 60 km,the basin extends to the upper mantle,which shows high velocity.Low velocity still occurs in this depth range in the lower crustal portion of the eastern margin of the plateau at an average velocity of 4.0～4.5 km/s.The prominent features of the VS profiles indicate that the majority of low-velocity zones appear in the middle crust at 20 km to 40 km and that small low-velocity zones occur in the upper crust at 10 km to 20 km and in the lower crust at 40 km to 60 km.In addition,only a portion of the low-velocity zone occurs in the southern region of eastern margin of the plateau.The crust varies in thickness from 50 km to 66 km in the eastern margin of the plateau and from 40 km to 44 km in the basin.The gradient of the Moho discontinuity is highest in the boundary along the eastern margin of the plateau toward the basin.The crustal flow does not increase,and most of the flow direction occurs along the main active faults.The effective middle and lower crustal thicknesses have been estimated to be between the 20 km and 40 km; the crustal viscous flow is generally heterogeneo

关 键 词：青藏高原东缘 地壳 上地幔 接收函数法 线性反演 S波速度结构 

分 类 号：P315.31[天文地球—地震学]