地球物理学进展 ›› 2018, Vol. 33 ›› Issue (6): 2193-2203.doi: 10.6038/pg2018BB0550

• 固体地球物理及空间物理学(大气、行星、地球动力学、重磁电及地震学、地热学) • 上一篇    下一篇

横观各向同性沉积谷地对平面qP和qSV波的放大作用

巴振宁1,2,喻志颖1,梁建文1,2,*()   

  1. 1. 天津大学土木工程系,天津 300072
    2. 滨海土木工程结构与安全教育部重点实验室,天津 300072
  • 收稿日期:2018-03-02 修回日期:2018-10-11 出版日期:2018-12-20 发布日期:2019-03-03
  • 通讯作者: 梁建文 E-mail:Liang@tju.edu.cn
  • 作者简介:巴振宁,男,1980年生,山东东营人,教授,博士,主要从事地震工程研究.(E-mail: Bazhenning_001@163.com)
  • 基金资助:
    国家自然科学基金资助项目资助(51578373);国家自然科学基金资助项目资助(16JCYBJC21600)

Amplification of plane qP and qSV waves by an alluvial valley based on the TI medium model

BA Zhen-ning1,2,YU Zhi-ying1,LIANG Jian-wen1,2,*()   

  1. 1. Department of Civil Engineering, Tianjin University, Tianjin 300072, China
    2. Key Laboratory of Coastal Structures in Civil Engineering and Safety of Ministry of Education, Tianjin 300072, China
  • Received:2018-03-02 Revised:2018-10-11 Online:2018-12-20 Published:2019-03-03
  • Contact: Jian-wen LIANG E-mail:Liang@tju.edu.cn

摘要:

采用间接边界元方法(IBEM)结合“分区契合”技术研究了横观各向同性(TI)介质沉积谷地对平面qP和qSV波的散射问题.方法中精确动力刚度矩阵的引入使得问题求解不受土层厚度的限制,而均布斜线荷载动力格林函数的引入避免了传统边界元方法中的奇异性问题,因而方法具有较高精度.文中通过与各向同性介质结果的比较验证了方法的正确性,并以各向同性单一土层半空间中梯形截面TI介质沉积谷地为例,在频域内进行了数值计算分析.研究表明:TI介质与各向同性介质沉积谷地对qP和qSV波的放大效应差异显著,TI介质参数对位移幅值的空间分布及其大小均有着重要的影响;TI介质参数的变化导致了谷地动力特性的改变,进而改变了谷地与半空间的动力相互作用机制,表现为不同TI介质参数对应的谷地表面位移幅值放大谱的峰值及其峰值频率均明显不同.为更精确的评估沉积谷地对地震动的放大效应,应充分考虑介质的TI性质.

关键词: 平面qP和qSV波, 横观各向同性, 格林影响函数, 沉积谷地

Abstract:

The scattering of plane qP and qSV waves in an alluvial valley with a Transversely Isotropic (TI) medium is studied by using the Indirect Boundary Element Method (IBEM) and the “conjunction” technique. The exact dynamic stiffness matrix method in the problem solving is not limited by the soil thickness. Dynamic Green’s function of uniformly distributed diagonal loads avoids the singular problem in conventional boundary element method, therefore gaining higher accuracy. The adopted method is verified by comparing the results of degenerated isotropic model with published ones, and numerical calculations are performed in the frequency domain regarding a TI trapezoid alluvial valley in an isotropic half-space. Result shows that the amplification effects of the TI medium and the isotropic medium sedimentary valley on the qP and qSV waves are significantly different and the parameters of TI medium have important influence on the spatial distribution and displacement amplitude. The different TI medium parameters can cause obvious changes in the dynamic characteristics of the valley, leading to the different dynamic interactions between the valley and the half-space. The peak value and frequency of the amplitude of the surface displacement of the different TI media parameters are obviously different. For a more accurate assessment of the amplification effect, the TI properties should be considered.

Key words: plane qP and qSV wave, Transversely Isotropic (TI), Green’s function, alluvial valley

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