中文摘要：

沉积河谷对地震波的高频散射规律尚不明确。采用一种高精度间接边界元法（IBEM）用于沉积河谷对平面P、SV和Rayleigh波的二维散射宽频求解分析。数值结果表明：IBEM可高效精确地模拟地震波的宽频散射;中低频段（无量纲频率η〈5.0）,河谷地形对地震波的放大效应显著;高频波段（η〉10.0）,河谷放大效应减弱甚至出现缩幅效应。随河谷深度增加,位移放大频段的带宽逐渐减小,第一峰值频率降低,且在低频段频谱曲线振荡剧烈。阻尼比对沉积河谷地表位移幅值具有显著影响,尤其是在高频段衰减作用明显。实际沉积河谷场地地震反应分析,需充分考虑波型、入射波频率和角度、河谷深宽比等因素,以更科学地进行震害解释和地震安全性评价。

英文摘要：

To date, the high frequency scattering has not been established. In this study, we ado method （IBEM） in a two-dimensional broadban law of seismic waves in sedimentary river valleys pt the high-precision indirect boundary element d analysis of P, SV, and Rayleigh waves. The numerical results demonstrate that the IBEM is effective and accurate in simulating seismic wave broadband scattering. In low and medium frequencies （dimensionless frequency η〈5.0）, the seis- mic wave amplification effect in valleys is significant, and it attenuates at high frequencies （η〉10.0） and even exhibits a necking effect. In terms of surface displacement amplitude, with a decrease in the incident angle θ, the maximum ground displacement amplitude shows a gradualdecreasing trend. The surface displacement amplitude changes more dramatically with increases in the incident frequency η. Meanwhile, the focusing effect of seismic waves in sedimentary valleys also has a significant impact. When the incident wave frequency increases, the sedimentary valley displacement amplitude variation range of the valley terrain is more intense. With an increase in the valley depth, the bandwidth in the displacement amplification frequency gradually decreases. with the frequency at first peak decreasing and the spectrum curve strongly oscillating at low frequency. With an increase in depth of the sedimentary valley, the bandwidth of the displacement amplification spectrum decreases, the frequency at the first peak is reduced, and in the low frequency band, the spectrum curve is sharp. The damping ratio has a significant impact on the surface displace- ment amplitude of the sedimentary valley, which clearly attenuates, especially at high frequency. To more scientifically interpret earthquake damage and to better evaluate seismic safety, seismic response analyses of actual sedimentary valleys must take several factors into consideration, including wave type, incident frequency, and angle, as well as the depth-to-width ratio of the valley.