| 青藏高原中部INDEPTH-III剖面低速层研究 |
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| 引用本文：牛潇,郑洪伟,贺日政,李娱兰,严江勇,李宗旭.2021.青藏高原中部INDEPTH-III剖面低速层研究[J].地球学报,42(1):74-84. |
| DOI：10.3975/cagsb.2020.071801 |
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| 基金项目: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) |
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| 中文摘要: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。 |
| 中文关键词:青藏高原 班公湖—怒江缝合带 接收函数分析 低速层 |
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| A Study of the Low Velocity Layer along INDEPTH-III Profile in Central Tibetan Plateau |
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| Abstract: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-III broadband 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. |
| keywords:Tibetan Plateau Bangong Co–Nujiang Suture receiver function analysis low velocity zone |
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