西藏西部地区的远震P波层析成像研究

樊杰 杨文采

樊杰,杨文采. 2022. 西藏西部地区的远震P波层析成像研究. 地震学报,44(4):567−580 doi: 10.11939/jass.20200168
引用本文: 樊杰,杨文采. 2022. 西藏西部地区的远震P波层析成像研究. 地震学报,44(4):567−580 doi: 10.11939/jass.20200168
Fan J,Yang W C. 2022. Structure of western Tibet from P wave teleseismic tomography. Acta Seismologica Sinica,44(4):567−580 doi: 10.11939/jass.20200168
Citation: Fan J,Yang W C. 2022. Structure of western Tibet from P wave teleseismic tomography. Acta Seismologica Sinica44(4):567−580 doi: 10.11939/jass.20200168

西藏西部地区的远震P波层析成像研究

doi: 10.11939/jass.20200168
详细信息
    通讯作者:

    樊杰,在读硕士研究生,主要从事层析成像方面的研究,e-mail:fanjiezju@zju.edu.cn

  • 中图分类号: P315.2

Structure of western Tibet from P wave teleseismic tomography

  • 摘要: 采用快速行进法正演计算了西藏西部地区的远震P波理论走时,随后基于该地区台阵提取到的相对到时残差利用子空间迭代算法反演得到该地区的地壳上地幔速度相对分布。层析成像结果显示:西藏西部地区在下地壳深度显示高速异常,上地幔深度该地区内部的高速异常范围从西往东逐渐减小,且研究区域东部存在高低速异常相间分布。据此认为印度板块在青藏高原内部近水平俯冲,西部俯冲范围较大,且俯冲过程中存在板块撕裂现象,撕裂的印度板块拆沉进入上地幔,而撕裂产生的间隙由于应力释放导致了西藏西部地区新生代裂谷的形成。

     

  • 图  1  西藏西部地区构造背景及本文所用台阵分布

    Figure  1.  Tectonic settings of western Tibet and the seismic arrays used in this study

    图  2  反演所用2 191个地震事件的分布

    Figure  2.  Distribution of 2 191 seismic events used in this study

    图  3  2007年7月18日18点01分25秒地震事件经预处理之后的波形展示

    Figure  3.  Seismic waveforms of an event occurred at 18:01:25 on July 18,2007 after pre-processing

    图  4  自适应叠加方法效果示意图

    (a) 基于AK135模型的初始对齐数据;(b) 10次迭代之后的对齐数据

    Figure  4.  Adaptive stacking example

    (a) Alignment of initial traces given by AK135 model;(b) Alignment of final traces achieved after ten iterations

    图  5  最优阻尼因子ε和光滑因子η的估计

    Figure  5.  Trade-off curves of optimum smoothing weight factor η and damping parameter ε

    图  6  基于CRUST1.0 (a)和CRUST2.0模型(b)获得的西藏西部地区在100 km和250 km深度处的地壳层析成像结果(深度标于子图的左下角,下同)

    Figure  6.  Tomography results of the crust in western Tibet at the depth of 100 km and 250 km based on CRUST1.0 (a) and CRUST2.0 (b) models. The depth is labeled at the lower-left corner of each subfigure,the same below

    图  7  初始模型(a)和最终模型(b)的相对到时残差分布图

    Figure  7.  Distribution of relative arrival time residuals for the initial (a) and final (b) models

    图  8  西藏西部层析成像棋盘格测试恢复结果(左上角为对比模型)

    Figure  8.  Checkerboard tests in this study (The compared model is on the upper-left)

    图  9  西藏西部不同深度(a—d)处的层析成像结果

    红色箭头代表俯冲过程中撕裂的印度板块

    Figure  9.  Tomography results of western Tibet at different depths (a−d)

    The red arrows represent the position of the torn Indian Plate

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出版历程
  • 收稿日期:  2020-10-26
  • 修回日期:  2021-01-03
  • 刊出日期:  2022-08-16

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