粘弹性浅圆弧形山谷地形对地震动谱特性的影响

Effect of Viscoelastic Local Canyon on the Spectrum Property of Ground Motion

基于凹陷地形对SV波的散射进行了分析,通过与解析解的对比,对所采用的数值算法进行了检验,然后利用钟形脉冲作为SH波输入,获得了浅圆山谷地形的地表响应,进而获得了不同观测点对自由场地点的谱比,并利用谱比研究了浅圆弧形山谷地形特征尺寸(深宽比)、波的入射角度以及介质阻尼效应等几个因素对地震动特性的影响。结果显示,浅圆弧形山谷地形的特征尺寸和地震波入射角度对地震动谱特性影响较大,影响程度与入射地震波频率有关。其中,入射角度的影响更显著。

We apply explicit finite difference method to analyze the topography effect of viscoelastic site. In order to test the method we have used in this paper, we introduce the development about this method and make a numerical experiment on scattering of SV waves for local canyon. Then we obtain the response of ground surface under the excitation of bell shape impulse. We study the influence of several factors including the characteristic size of canyon （ ratio of depth to width）, the angle of incidence of impulse wave and the medium damping on spectrum property of ground motion. For a shallow canyon, the characteristic size and the angle of incidence have great effect on spectrum property of ground motion, and the extent of effect is related to the frequency of basic excitation. The effect of angle of incidence is more distinct than that of charaeteristic size.