用HV谱比法推测银川市区沉积层基底分布特征

在缺乏其他资料的情况下,地脉动常常用做确定地震动对地表介质产生影响效应的简便手段。本文以银川市区为研究对象,根据地震勘探资料有目的的选取5条测线在银川市区进行地脉动观测,观测点共141个。用Nakamura提出的HV谱比法解析观测数据,在给定地下构造剪切波速度(VS)的基础上,由H/V比值曲线中的基本频率推测盆地深层地下构造。通过理论计算进一步验证了解析结果。结合前人地震勘探资料推测了银川市区脉动基本频率分布特征,并给出2D和3D银川市基底构造变化情况,对比分析表明,HV谱比法得到的脉动基本频率值可以反映银川盆地基底变化情况。

Using the HV Spectral Ratio Method to Speculate the Underground Structure Distribution Characteristics of Yinchuan City

Miccrotremor is often used as an easy way to make certain how much influence effect that earthquake motion brought to the surface geology without or with a few other data.Yinchuan city is the research area.The spectral ratio between the horizontal components of microtremor relative to the vertical component,H/V,is used to deduce the basin's structure whose thickness could reach a few kilometers,through dense microtremor observation independently.Based on the seismic prospecting data,5 observation lines are selected,intentionally to make the microtremor observation in Yinchuan city and there are 141 observation points.The observation area including Xingqing,Jinfeng and Xixia districts,which covers all of the Yinchuan city.The computation method is HV spectral ratio proposed by Nakamura,and the autocorrelation analysis is used to calculate the value of the spectral ratio between the horizontal components of microtremor relative to the vertical component.The deep underground structure of the Yinchuan basin is speculated by the fundamental frequency value obtained from the HV line,based on the presumed average S wave velocity.The theoretical calculation shows that HV method is credible.The basic spectrum distribution figure of Yinchuan city and its relevant 3D distribution figure are presumed combined with the seismic prospecting data,which shows that the fundamental frequency calculated by the HV spectral ratio method can explain the underground structure change of Yinchuan city.