向家坝库首区地脉动与水库泄洪激发的振动特征分析

Analysis of earth microtremor in head area of Xiangjiaba Reservoir and vibration characteristics excited by flood discharge of the reservoir

利用宽频带数字测震仪监测的金沙江下游水库区常时地脉动和水库泄洪激发的振动记录,分析研究给出:常时地脉动信号出现在高频段1.9~12.0 Hz;相对应的卓越周期0.08~0.52 s。水库泄洪激发地动的信号包含多种振动和噪声成份,与常时地脉动信号相比,其出现在低频段,呈现出更长的周期。2012年10月向家坝水库泄洪激发的地动幅度值,随观测站离坝址距离的增大而衰减;坝址峰值加速度均值为1.9 mm/s2;峰值速度均值为0.08 mm/s;最大位移均值为95μm;仪器烈度值为4度,这与现场调查结果一致。

Ground vibration excited by earth microtremor and flood discharge was monitored by broad band digital seismograph in the reservoir area of Jinsha River downstream.Based on the vibration records,some useful analysis conclusions are given in this paper.Earth microtremor appears in high frequency range from 1.9 Hz to 12.0 Hz and the corresponding predominant period is from 0.08 s to 0.52 s.Compared with ordinary earth microtremor,ground vibration exited by flood discharge consists of various vibration signals and noise,and has lower frequency band and longer period.The ground vibration recorded during the flood discharge of Jinsha River in October 2012 show that,the vibration amplitude decreases with the distance increasing from dam site,and at the dam site,the average peak acceleration is 1.9mm /s2;the average peak velocity is 0.08mm /s,and the average value of maximum displacement is 95 μm;the instrument intensity is degree Ⅳ.All these are consistent with the field investigation results.