SV波斜入射下成层盆地地震动时-频域放大特征研究  

Study on amplification characteristics of ground motion in layered basin in time and frequency domain under oblique incidence of SV wave

作　　者：魏成前 于彦彦[1] 丁海平[1] WEI Chengqian;YU Yanyan;DING Haiping(Key Laboratory of Structure Engineering of Jiangsu Province,Suzhou University of Science and Technology,Suzhou 215011,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215011

出　　处：《地震工程与工程振动》2022年第2期225-234,共10页Earthquake Engineering and Engineering Dynamics

基　　金：国家自然科学基金青年基金项目(51808371);江苏省高等学校自然科学研究面上项目(18KJB560017);江苏省结构工程重点实验室开放研究课题(ZD1703)。

摘　　要：基于二维成层盆地模型,以盆地不同场点对应的一维等效土层模型的结果为参考,采用有限元法与人工透射边界相结合的方法,研究了SV波入射时入射角θ对盆地地表地震动放大特征的影响。结果表明入射角度和盆地分层构造对地表地震动放大特征均有显著影响:(1)盆地地表地震动峰值受θ影响显著,不同分量、不同区域(盆地边缘和内部区域)的位移峰值随入射角的变化规律也不同;(2)入射角度对盆地边缘效应出现的位置影响明显。随θ增大,水平分量出现位置从盆地斜边范围之外转移至斜边范围内,垂直分量边缘效应的位置不受入射角影响;(3)相比一维等效土层模型,水平分量地震动放大系数在盆地左侧边缘区域最大(1.45左右),且随θ增大而增大,右侧与之相反;垂直分量放大系数随θ的增大而减小,但左右两侧放大系数基本相同;(4)从盆地边缘向盆地内部,观测点时程的主频从高向低变化。在不同入射角下其谱比曲线特征相似,但谱比值均随入射角度的增大而增大。不同θ角下成层盆地边缘和内部区域主要放大频段差别显著;(5)相比均匀盆地,成层盆地地震动受入射角影响更加强烈,地震动峰值分布特征也显著不同。Based on the 2D layered basin model,and using the results of the one-dimensional equivalent soil model corresponding to different field points in the basin as a reference,the influence of incidence angleθof SV waves on the basin ground motion are studied by using the finite element method and artificial transmitting boundary.The re⁃sults show that the angle of incidence and the stratified structure of the basin have significant impacts on the charac⁃teristics of ground motion amplification:(1)The peak of the ground motion of the basin is significantly affected byθ,and the peak displacement of different components and regions(basin edges and internal regions)demonstrate different changing features withθ.(2)The incident angle has a significant influence on the location where the basin edge effect appears.Asθincreases,the position of the horizontal component shifts from hypotenuse outside range to the within range of the basin,while the position of the edge effect of the vertical component is not affected by the incident angle.(3)Compared with the one-dimensional equivalent soil layer model,the amplification factor of hori⁃zontal component is the largest in the left edge of the basin(about 1.45),and it increases with the increase ofθ,while the right side is the opposite;the vertical component amplification factor decreases with the increase ofθ,but the magnification coefficients on the left and right sides are basically the same.(4)From the basin edge to the basin internal region,the dominant frequency of the observation point changes from high to low.The characteristics of the spectral ratio curves are similar for different incident angles,but the spectral ratio values all increase with growing incident angle.There are significant differences in the main amplification frequency bands at the edge and internal areas of stratified basins under differentθangles.(5)Compared with homogeneous basins,stratified ba⁃sins are more strongly affected by the angle of incidence,and the distribution characteristics

关 键 词：成层盆地 有限元法 透射边界 入射角度 放大效应 

分 类 号：P315.9[天文地球—地震学]