青藏高原东缘岩石圈及软流圈结构  

Lithosphere and asthenosphere structure on eastern margin of Qinghai-Tibet Plateau in China

作　　者：范军[1,2] 朱介寿[1] 江晓涛[1] 吴朋[2] 杨宜海[1] 

机构地区：[1]成都理工大学地球物理学院,成都610059 [2]四川省地震局,成都610041

出　　处：《成都理工大学学报（自然科学版）》2015年第6期746-752,共7页Journal of Chengdu University of Technology: Science & Technology Edition

基　　金：国家自然科学基金重点项目(40839909);国家自然科学基金项目(41074062)

摘　　要：青藏高原东缘岩石圈及软流圈结构的研究是认识该区域地壳上地幔的构造形变及高原内部物质向东运移的重要手段。通过搜集四川区域数字地震台站和野外临时地震台站记录的观测资料，采用接收函数共转换点（CCP）偏移叠加成像方法对青藏高原东缘深部结构研究。研究结果揭示：青藏高原东缘的地壳厚度比四川盆地的魂壳厚度大10～20km在青藏高原东缘与四川盆地的过渡地带，莫霍面处存在大幅度的垂向错断和变形。从青藏高原东缘到四川盆地，岩石圈与软流圈分界面（LAB）显示出深度逐步增加、410km间断面深度则有变浅的趋势。在地壳的下界面和LAB界面间以及LAB界面与410km间断面间也存在多条不连续的分层。青藏高原东缘和四川盆地的LAB界面的下方都有明显的低速层分布，但它们之间存在差别，四川盆地的LAB界面的下方低速层分布较为完整，而青藏高原东缘LAB界面下方的低速层分布中可见离散的高速块体分布。青藏高原东缘与四川盆地深部结构的明显差异，体现了该地区的深部地球动力学背景的复杂性。Study the structure of the lithosphere and the asthenosphere on the eastern margin of Qinghai Tibet Plateau is the basis to recognize the tectonic deformation and the movement form of the internal materials in the crust and the upper mantle. Using the earthquake observation data of the Sichuan Digital Seismic Network and the mobile broadband seismic stations, and the receiver function common conversion point （CCP） migration stack imaging method, this paper studies the deep structure on the east margin of Qinghai-Tibet Plateau. The results show that the thickness of the crust on the eastern margin of Qinghai-Tibet Plateau is deeper than that of Sichuan Basin, about l0b 20 kin. In the transition zone on the eastern margin of Qinghai-Tibet Plateau and Sichuan Basin, at the Moho interface there exists large vertical offsets and deformation. The lithosphere and asthenosphere boundary （LAB） discontinuity presents the deepening of the depth gradually, and 410 km discontinuity depth also has the trend of decreasing the depth from Sichuan Basin to Qinghai-Tibet Plateau. There are multiple discrete layers tilt to the west between the lower crust discontinuity and LAB discontinuity. And there are also multiple discrete layers between LAB discontinuity and 410 kmdiscontinuity, but the extent of tilt to the west is less. Tibet Plateau beneath LAB discontinuity present the Sichuan Basin and the east margin of Qinghai- low-velocity layer distribution obviously, but there is a difference between them. The low-velocity layer distribution in Sichuan Basin is relatively complete, but on the east margin of Qinghai-Tibet Plateau, there is the discrete high-velocity block distribution in the low-velocity layer. The distinct difference in the deep structure of the eastern margin of Qinghai-Tibet Plateau and Sichuan Basin reflects the complexity of the deep geodynamic background in this region.

关 键 词：青藏高原东缘 接收函数 共转换点偏移叠加 岩石圈 软流圈 

分 类 号：P542.5[天文地球—构造地质学] P631.44[天文地球—地质学]