考虑阻抗比影响的三维沉积盆地地震动时-频放大特征  

Time-frequency amplification characteristics of ground shaking in 3-D sedimentary basins considering the influence of impedance ratio

作　　者：吴烨钦 于彦彦[1] 丁海平[1] WU Yeqin;YU Yanyan;DING Haiping(Suzhou University of Science and Technology,Key Laboratory of Structure Engineering of Jiangsu Province,Suzhou 215009,China)

机构地区：[1]苏州科技大学江苏省结构工程重点实验室,江苏苏州215009

出　　处：《世界地震工程》2023年第3期129-141,共13页World Earthquake Engineering

基　　金：国家自然科学基金青年基金项目(51808371)。

摘　　要：基于三维谱元法模拟了三维沉积盆地模型在点源作用下的地震动响应,通过分析地表速度峰值、放大系数以及特征频率处的谱比分布,研究了不同阻抗比(IR)下盆地的地震动放大特征。结果表明:1)地震动峰值并非随阻抗比的增加而单调递减,且最强烈地震动位置均随阻抗比的减小而向盆地内部移动。2)地震动放大系数与峰值分布总体一致,IR在0.08~0.44的范围内,盆地地表地震动幅值可达基岩半空间地震动幅值的3.68倍。但小阻抗比时三维盆地地震效应会引起某些分量上放大系数的显著不同的分布特征。3)最大放大频率随阻抗比而变化,IR=0.26~0.33时的主要放大频率为IR=0.08时的3倍。4)三维盆地地震效应、阻抗比和一维等效自振频率共同决定了盆地地震动的时-频域放大特征。比较而言,阻抗比较小时更应考虑三维盆地的地震效应。Based on the 3D spectral element method,the ground vibration response of a 3D sedimentary basin model under the action of point sources is simulated,and the ground vibration amplification characteristics of the basin under different impedance ratios(IR)are studied by analyzing the peak surface velocity,amplification coefficients and the spectral ratio distribution at the characteristic frequencies.The results show that①the peak value of ground shaking is not monotonically decreasing with increasing impedance ratio,and the location of the strongest ground shaking moves to the inner part of the basin with decreasing impedance ratio.②The amplification coefficient of ground shaking is generally consistent with the peak distribution,and the IR is in the range of 0.08-0.44,and the ground shaking amplitude at the surface of the basin can be 3.68 times of the ground shaking amplitude in the bedrock half space.However,the 3D basin seismic effects at small impedance ratios cause significantly different distribution characteristics of amplification coefficients on certain components.③The maximum amplification frequency varies with the impedance ratio,and the main amplification frequency at IR=0.26~0.33 is three times of that at IR=0.08.④The 3D basin seismic effect,impedance ratio,and 1D equivalent self-oscillation frequency jointly determine the time-frequency domain amplification characteristics of basin ground shaking.For comparison,the seismic effect of the 3D basin should be considered more when the impedance ratio is small.

关 键 词：谱元法 三维盆地 阻抗比 时-频域 放大系数 

分 类 号：P315.9[天文地球—地震学]