三维地形中地震动的频域特征——以芦山地区为例

The Characteristics of Frequency Domain of Ground Motion in 3-D Topography——A Case Study of Lushan Area

地形条件对局部震害分布有重要影响。本文选择地形起伏剧烈的芦山地区,采用三维谱元法模拟地震波传播。研究了该地区地震动的频谱特征。计算了测线上位于山顶和山谷的台站傅里叶频谱,并研究了各自的谱值和谱值比特征。分析结果表明:山顶包含了较高的频谱;山谷包含了较低的频谱;山顶上的频谱值高于山谷的频谱值;并且地形对水平分量的影响更大。同时,进一步从频谱中提取了峰值放大比和峰值频率2个参数,分析了其在芦山地形中的分布特征。结果显示,山顶对应了较大的峰值放大比和峰值频率,而山谷则对应了较低的峰值放大比和峰值频率。

The topography plays an important role in local disaster distribution. In this article, Lushan area with steep topography is chosen as our research area. We use 3-D spectral element method to simulate seismic wave propagation and analyze the spectrum of strong ground motion. We calculate the spectrum of velocity time history of stations on ridge and valley of selected profiles. The results show that the spectrum on ridge contains higher frequency and spectrum on valley contains lower frequency. Spectrum on ridge are larger than spectrum on valley, and the surface irregularity has greater effect on horizontal components. Moreover, we calculate the peak amplification ratio and peak frequency from the spectrum and analyze their distribution on Lushan topography. The results show that the ridge has larger amplification ratio and peak frequency while the valley has lower ratio and peak frequency.