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含覆盖层峡谷对地震波的高频散射规律尚不明确.本文采用间接边界元方法(IBEM)分析半空间中含覆盖层峡谷地形对地震波的二维宽频散射,对入射波型、入射角度和频率、覆盖层深宽比等因素对覆盖层地震响应规律的影响进行探讨分析.结果表明:IBEM可高效精确地对地震波的散射进行宽频模拟.对中低频段(无量纲频率η<5.0),含覆盖层峡谷地形对地震波的放大效应显著.对高频波段(η>10.0),覆盖层放大效应减弱甚至出现缩幅效应.随覆盖层深度增加,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.另外,覆盖层形状和入射角度对地震波聚焦特征也具有重要影响,不同波型入射下聚焦区域有很大差别.实际含覆盖层峡谷地形地震反应分析需精细考虑波型、入射波频率和角度、覆盖层深宽比等因素,以更科学地进行震害解释和地震安全性评价.
The high frequency scattering law of seismic waves in overburden canyon is not clear.In this paper, the indirect boundary element method (IBEM) is used to analyze the two-dimensional wide-band scattering of seismic waves in overlay canyons in half-space, and the effects of incident wave form, incident angle and frequency , The aspect ratio of the overburden, etc. The results show that the IBEM can simulate the scattering of seismic waves with high efficiency and accuracy.With the low frequency band (dimensionless frequency η <5.0), including The amplifying effect of the canyon topography on the seismic waves is remarkable. For the high frequency band (η> 10.0), the amplifying effect of the overburden is weakened or even reduced. With the increase of the depth of cover layer, the bandwidth of the amplifying band of the displacement decreases gradually. The first peak And the frequency is low, and the oscillation in the low-frequency spectral curve is violent. In addition, the shape and incident angle of the overburden also have an important influence on the focal characteristics of seismic waves, and the focal regions under different incident waveforms have great differences. The factors such as wave form, frequency and angle of incident wave, aspect ratio of overburden and so on should be carefully considered to make more scientific explanation of seismic damage and seismic safety .