不同散射模式下S波包络合成

景月岭 何李浩 李明会 张宇璇 郑司元

景月岭,何李浩,李明会,张宇璇,郑司元. 2021. 不同散射模式下S波包络合成. 地震学报,43(6):679−689 doi: 10.11939/jass.20200208
引用本文: 景月岭,何李浩,李明会,张宇璇,郑司元. 2021. 不同散射模式下S波包络合成. 地震学报,43(6):679−689 doi: 10.11939/jass.20200208
Jing Y L,He L H,Li M H,Zhang Y X,Zheng S Y. 2021. S wave envelope synthesis based on different scattering patterns. Acta Seismologica Sinica,43(6):679−689 doi: 10.11939/jass.20200208
Citation: Jing Y L,He L H,Li M H,Zhang Y X,Zheng S Y. 2021. S wave envelope synthesis based on different scattering patterns. Acta Seismologica Sinica43(6):679−689 doi: 10.11939/jass.20200208

不同散射模式下S波包络合成

doi: 10.11939/jass.20200208
基金项目: 中央高校基本科研业务费专项资金(PA2019GDPK0036)和清华大学水沙科学与水利水电工程国家重点实验室开放基金(sklhse-2020-D-04)共同资助
详细信息
    通讯作者:

    景月岭,e-mail:jing@hfut.edu.cn

  • 中图分类号: P315.3+1

S wave envelope synthesis based on different scattering patterns

  • 摘要: 为揭示地震波在地壳小尺度非均匀介质中的散射过程,更准确地描述地震波的包络展宽现象,本文基于多次各向异性散射理论,采用离散波数法求解能量密度积分方程,选取高斯型自相关函数表征的散射模式,得到S波能量密度包络。基于此,本文首先分析了单次散射和多次散射在形成S波能量密度包络中的贡献规律;然后探讨了吸收系数和总散射系数对合成S波能量密度包络的影响;最后对比了在不同散射模式下合成的S波能量密度包络的差异。结果显示:① 不同的散射模式下单次散射和多次散射对地震波散射过程的贡献规律是一致的,对于近震(震源距小于100 km),单次散射模型可以近似合成S波能量密度包络;随着震源距增大,多次前散射模型可以更快地接近总能量密度包络;② 吸收系数增大会降低直达S波和尾波幅值,总散射系数增大会降低直达S波幅值,但使得S波尾波幅值升高;③ 前散射模式下S波能量密度包络随震源距的增大会导致峰值延迟,包络展宽,尾波衰减一致性更快等现象产生。

     

  • 图  1  轴对称各向异性散射示意图(Sato,1995

    Figure  1.  A schematic plot of axially symmetric multiple anisotropic scattering process (Sato,1995

    图  2  引入震源特征时间函数的辐射传输理论示意图

    Figure  2.  The schematic view of radiative transfer theory with the source characteristic time function

    图  3  直达波 (a)、单次散射波 (b)、多次散射波 (c)的示意图

    Figure  3.  The schematic view of direct wave, single scattering wave and multiple scattering wave

    图  4  数值示例中使用的散射模式

    Figure  4.  The scattering patterns used in the numerical examples

    图  5  高斯型散射模式表征系数μ取为−2.0 (a),0 (b)和7.0 (c)时不同震源距r的散射结果比较

    Figure  5.  Comparison of scattering results at different hypocentral distances r when the Gaussian scattering pattern characterization coefficient μ=−2.0 (a),μ=0 (b) and μ=7.0 (c)

    图  6  不同散射模式下吸收系数ηi和总散射系数g0对S波能量密度包络合成的影响

    Figure  6.  Influence of absorption coefficient and total scattering coefficient on the synthesis of S wave energy density envelope under different scattering patterns

    图  7  不同散射模式下合成的S波能量密度包络

    (a) 前散射和各向同性散射模式;(b) 各向同性散射和后散射模式。图中纵坐标均为S波能量密度乘震源距系数exp (tS/15)后的结果

    Figure  7.  The energy density envelope of S wave synthesized in different scattering patterns

    (a) The forward scattering and isotropic scattering patterns;(b) The isotropic scattering and back scattering patterns。The ordinates in the figure are the results of S-wave energy density multiplied by hypocentral distance coefficient exp (tS/15)

    图  8  不同散射模式下合成的 S 波能量密度包络衰减一致性

    (a) 各向同性散射模式; (b) 后散射模式;(c) 前散射模式

    Figure  8.  The consistance of the energy density envelope attenuation for the S wave synthesized in different scattering patterns

    (a) The isotropic scattering pattern; (b) The back scattering pattern; (c) The forward scattering pattern

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出版历程
  • 收稿日期:  2020-12-21
  • 修回日期:  2021-04-22
  • 网络出版日期:  2021-12-06
  • 刊出日期:  2021-12-31

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