频率波数域内地壳层半空间剪切位错源宽频地震波传播模拟  

Simulation of broadband seismic wave propagation in a crustal half-space in frequency-wavenumber domain generated by shear dislocation sources

作　　者：梁建文[1,2] 吴孟桃 巴振宁[1,2] LIANG Jianwen;WU Mengtao;BA Zhenning(State Key Laboratory of Hydraulic Engineering Simulation and Safety,Tianjin University,Tianjin 300350,China;Department of Civil Engineering,Tianjin University,Tianjin 300350,China)

机构地区：[1]天津大学水利工程仿真与安全国家重点实验室,天津300350 [2]天津大学土木工程系,天津300350

出　　处：《岩石力学与工程学报》2022年第3期543-558,共16页Chinese Journal of Rock Mechanics and Engineering

基　　金：国家自然科学基金资助项目(52178495,51778413)。

摘　　要：剪切位错源地震波传播模拟是近断层地震动研究的理论基础,然而现有确定性方法在高频地震动求解和跨尺度计算中存在一定的不足。提出一种剪切位错源宽频地震波多尺度传播模拟的频率-波数域方法,能有效解决从高波速地壳尺度(公里级)到低波速岩土尺度(米级)成层半空间宽频(覆盖0.1~10 Hz的工程结构敏感频段)地震响应问题。利用Fourier-Hankel变换将柱坐标系下的三维波动方程由时间-空间域转换到频率-波数域内,并结合震源作用处的位移-应力间断条件,由修正刚度矩阵方法求得位错源引起的黏弹性层状半空间动力响应。首先与经典Haskell方法比较验证提出方法的正确性和精度,进而建立天津地区地壳结构中跨尺度场地模型,重点讨论震源频率和近地表软弱夹层对地震地面运动的影响。研究结果表明:(1)新方法在宽频地震动和含低波速细分土层的模拟中十分适用,能够清晰观测到位错源作用下地震波在层界面的反射、转换和透射等复杂传播过程及引起的地面运动特征;(2)软弱场地地面运动受震源频率影响明显,高频地震动作用使得地震辐射能量强度及范围增大,或将导致更为严重的地面破裂和结构破坏;(3)不同埋深和厚度的近地表软夹层对软弱场地地震反应均有重要影响,场地“滤波放大”和软夹层“隔震”的叠加使得地表响应变得十分复杂。Simulation of seismic wave propagation generated by shear dislocation sources is a theoretical basis for near-fault ground motion researches. However,existing deterministic methods have certain shortcomings in high-frequency solutions and cross-scale calculations. This paper proposes a frequency-wavenumber method for multi-scale modelling of broadband seismic wave propagation in the stratified half-space due to dislocations,which can effectively solve the broadband seismic response problem(covering 0.1-10 Hz engineering structure sensitive frequencies) from high-velocity crustal scale(kilometre level) to low-velocity geotechnical scale(metre level). The Fourier-Hankel transformation is used to convert the 3 D wave equations from time-space domain to frequency-wave number domain in the cylindrical coordinate system,and the dynamic response of a viscoelastic layered half-space due to a dislocation source is derived by the modified stiffness matrix method in conjunction with the displacement-stress discontinuity conditions. The correctness and accuracy of the proposed method are first verified by comparing with the classical Haskell method,and then a cross-scale site model embedded in the Tianjin crustal structure is established to focus on the effects of the source frequency and the near-surface soft interlayer on earthquake ground motions. The results show that the new method is very suitable for modelling broadband ground motions and low-velocity subdivided layers,and the complex propagation processes such as reflection,conversion and transmission of seismic waves at layer interfaces as well as the ground motion characteristics due to dislocation sources can be clearly observed. The ground motions of soft sites are significantly affected by the source frequency,and the high frequency excitation can increase the intensity and extent of the earthquake radiation energy,which may lead to more serious surface rupture and structural damage.The near-surface soft interlayers with different buried depths and thicknesses h

关 键 词：地震工程 剪切位错 地震动输入 频率–波数域方法 宽频地震动 跨尺度模拟 

分 类 号：P315[天文地球—地震学]