地球物理学进展 ›› 2018, Vol. 33 ›› Issue (5): 1862-1870.doi: 10.6038/pg2018BB0564

• 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

第四系剪切波速及品质因子对汶川地震中四川盆地地震效应的影响

于彦彦1(),丁海平1,刘启方2   

  1. 1. 江苏省结构工程重点实验室(苏州科技大学),江苏苏州 215011
    2. 中国地震局工程力学研究所,哈尔滨 150080;
  • 收稿日期:2017-12-22 修回日期:2018-07-16 出版日期:2018-10-20 发布日期:2019-01-11
  • 作者简介:于彦彦,男,1986年生,河南周口人,讲师,博士,研究方向为场地地震效应.
  • 基金资助:
    国家自然科学基金(51278323);国家自然科学基金(51378479);国家科技支撑计划课题(2015BAK17B01)

Effects of shear-wave velocity and quality factor of the Quaternary sediment on seismic effects of the Sichuan basin during the Wenchuan earthquake

YU Yan-yan1(),DING Hai-ping1,LIU Qi-fang2   

  1. 1. Key Laboratory of Structure Engineering of Jiangsu Province,Suzhou University of Science and Technology, Jiangsu Suzhou 215011, China
    2. Institute of Engineering Mechanics, China Earthquake Administration, Harbin 150080, China
  • Received:2017-12-22 Revised:2018-07-16 Online:2018-10-20 Published:2019-01-11

摘要:

基于已建立的三维四川盆地模型,利用谱元方法和并行计算技术研究了第四系介质的剪切波速及品质因子对汶川地震中四川盆地对于长周期地震波放大效应的影响.结果表明:剪切波速对盆地地震效应影响显著.对于水平分量,随着剪切波速的减小,成都平原内部,尤其是局部凹陷区域的强地震动的幅值及范围均显著增大,持时增长,强地震动场的分布特征也发生变化;同时,覆盖层边缘产生的面波增强,面波和体波的干涉使得波传播行为更加复杂;但垂直分量的地震动受剪切波速的影响较小.品质因子Q对盆地内地震动的影响相对较小.Q减小时,盆地内的地震动幅值及强地震动区域的范围略微变小,同时产生的面波的强度减弱,传播距离变短;但强地震动的位置及总体分布特征基本不变,放大系数的变化也较小.以上表明在四川盆地地震动场的模拟中,应重点关注盆地的速度构造,而对于品质因子可做适当假定.

关键词: 四川盆地, 第四系, 剪切波速, 品质因子, 汶川地震, 放大作用

Abstract:

Based on the established three-dimensional Sichuan basin model, and by using the spectral-element method and the parallel computing technique, effects of the shear-wave velocity (Vs) and the quality factor (Q) of the Quaternary sediments on low frequency (<0.5 Hz) wave amplification behaviors of the Sichuan basin during the Wenchuan earthquake were investigated. The results show that Vs has significant effect on basin amplification behavior. For the horizontal component, with the decreasing of Vs, the strong motion amplitude and its area of the Quaternary Chengdu plain increase obviously, following with lengthened duration time and changed strong motion distribution feature. Meanwhile, Surface waves generated at the sediment edge were enhanced, and the interference between surface and body waves makes the wave propagation behavior more complex. In addition, strong ground motion of the vertical component was insensitive to the variations of Vs. The quality factor Q has less influence on the basin internal ground motion compared with shear wave velocity. with the decreasing of Q, the strong motion amplitude and its area become slightly smaller, and the surface waves were weakened, with smaller travelling distance. However, the location of the strongest ground motion and its general distribution pattern were almost unchanged. The variation of basin amplification factor can also be ignored. These results suggest that in the numerical simulation of basin seismic effects, emphasis should be paid on the velocity structure, and proper assumptions can be made for the quality factor.

Key words: Sichuan basin, Quaternary, shear wave velocity, quality factor, Wenchuan earthquake, amplification effect

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