泸定磨西台地场地地震效应研究

Site Seismic Effect of the Moxi Platform in Luding,Sichuan

基于在泸定磨西台地获取的地脉动数据,采用水平与垂直谱比法(HVSR法),开展了磨西台地场地地震效应研究。结果表明:(1)磨西台地地脉动频谱特征明显,0.2~15Hz内的峰值频段容易识别,大部分测点的峰值频率集中在1Hz左右,场地土层卓越频率范围0.80~1.34Hz,地层岩性和覆盖层厚度对卓越频率的影响作用较大;(2)磨西台地场地放大效应较为显著,绝大部分测点的峰值放大系数都大于2,与场地土层卓越频率相对应的峰值放大系数介于2.69~6.97;(3)磨西台地地层具有明显的地震效应方向性特征,100°~150°和150°~190°是磨西台地场地地震效应的两个优势方向区间,地层岩性差异对优势方向的控制作用较为突出。研究成果填补了磨西台地场地地震效应研究的空白,为深入开展冰川堆积物地层动力响应研究提供了新的途径,也为泸定6.8级地震后磨西台地所在乡镇的规划与重建提供了参考。

Based on the microtremor data obtained at the Moxi Platform in Luding,we studied the site seismic effect of the Moxi Platform by using the horizontal-to-vertical spectral ratio method(HVSR).As the results show:(1)The microtremor spectrum characteristics of the Moxi Platform are obvious,and the peak frequency band between 0.2Hz and 15Hz is easy to identify.The peak frequency of most measuring points is around 1Hz,and the predominant frequency of the soil layer in the study site ranges from 0.80Hz to 1.34Hz,which is obviously affected by the stratum lithology and the overburden thickness.(2)The site amplification effect of the Moxi Platform is relatively significant,with the peak amplification coefficient of most measuring points being greater than 2,and the peak amplification coefficient corresponding to the predominant frequency of the soil layer in the study site is between 2.69 and 6.97.(3)The strata of the Moxi Platform have obvious seismic effect directional characteristics,and the two dominant directions are 100°~150°and 150°~190°,which are mainly controlled by the difference of the stratum lithology.The research results in this paper fill in the blank of research on the site seismic effect of the Moxi Platform.They could provide a new way for in-depth research on the dynamic response of glacial deposits and a reference for the post-earthquake planning and reconstruction of the township located in the Moxi Platform.