青藏高原中部INDEPTH-Ⅲ剖面低速层研究  

A Study of the Low Velocity Layer along INDEPTH-ⅢProfile in Central Tibetan Plateau

作　　者：牛潇 郑洪伟[2] 贺日政[1] 李娱兰 严江勇 李宗旭 NIU Xiao;ZHENG Hong-wei;HE Ri-zheng;LI Yu-lan;YAN Jiang-yong;LI Zong-xu(SinoProbe Center-China Deep Exploration Center,Chinese Academy of Geological Sciences,Beijing 100037;Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037;School of Earth and Space Sciences,University of Science and Technology of China,Hefei,Anhui 230026)

机构地区：[1]中国地质科学院地球深部探测中心,北京100037 [2]中国地质科学院地质研究所,北京100037 [3]中国科学技术大学地球和空间科学学院,安徽合肥230026

出　　处：《地球学报》2021年第1期74-84,共11页Acta Geoscientica Sinica

基　　金：国家自然科学基金项目(编号:41761134094,41574086,41274095);国家重点研发计划项目(编号:2016YFC0600301,2018YFC0604102);中国地质调查局地质调查项目(编号:DD20190015)联合资助。

摘　　要：印度大陆板块北向碰撞及俯冲导致的青藏高原快速隆升,使得青藏高原内部的物质组成及构造演化更为复杂,其中之一高原内部的低速层分布特征及其构造成因尚不明确。藏北高原中部的班公湖—怒江缝合带两侧宽频带地震观测程度较高,为调查班公湖—怒江缝合带两侧低速层分布特征提供了良好的客观条件。本文选取了INDEPTH-Ⅲ项目布置在班公怒江缝合带两侧的宽频带地震台站记录的远震数据,开展接收函数分析,通过时频域相位滤波提高信噪比,并利用接收函数复谱比非线性反演方法得到了台站下方一维S波速度结构。反演结果表明班公湖—怒江缝合带两侧地壳中低速层广泛分布,且横向不连续,埋深在20~40 km之间,部分地区在0~15 km的上地壳也出现低速层。上地壳内的低速层分布特征主要与地表区域构造及沉积层分布相关;中下地壳内的低速层分布不仅受到了地体边界的约束,且可能与后期青藏高原整体隆升相关。The northward collision and subduction of the Indian continental plate led to the rapid uplift of the Tibetan plateau.As a result,the material composition and tectonic evolution in the plateau are the most complex,and hence the distribution characteristics and tectonic origin of the low-velocity strata are still unclear.The broad-band seismic observations are relatively high on both sides of the Bangong Co–Nujiang Suture zone(BNS)in the central part of northern Tibetan Plateau,which provides a good condition for investigating the distribution of low-velocity layers.In this paper,the authors selected the teleseism data recorded by INDEPTH-Ⅲbroadband seismic stations deployed on both sides of the BNS to the receiver function analysis.The authors improved the signal-to-noise ratio through time-frequency domain phase filtering,and obtained the one-dimensional S-wave velocity structure characteristics under each station by use of the nonlinear inversion method of the complex spectrum ratio of the receiver function.The results obtained by the authors show that a discontinuous low velocity layer with the depth of 20~40 km is widely distributed within the crust beneath both sides of the BNS,and low velocity layers also appear in 0~15 km nearby the subsurface.Comparisons show that the distribution pattern of low-velocity layers in the upper crust is mainly related to the surface regional structure,like east-western trend thrust fault zone and surface sediments,while low-velocity layers in the middle and lower crust not only are constrained by the boundary of the terrane but also possibly related to the Tibetan Plateau uplifting.

关 键 词：青藏高原 班公湖—怒江缝合带 接收函数分析 低速层 

分 类 号：P631[天文地球—地质矿产勘探]