天水市建筑场地地面脉动特征

通过对天水市建筑场地地面脉动的观测与分析,说明地面脉动幅值受多种因素的影响,並随地形地貌的改变而变化。水平向脉动明显地有一个卓越方向,水平振动的卓越方向在整体上受场地周围的地形所约束,局部场地条件只具有次要的影响。地面脉动频谱特性一般是在大区域范围内才能反应出变化来,且受区域地质和新构造运动的情况所控制,地面脉动的特征是局部地形地貌对谱型的影响迭加在区域背景上的结果。地面脉动与强震时地面运动特征的对比及二者的相关性是今后研究场地地面运动的重要问题。按场地地面脉动的卓越周期和谱型将测区场地作了区段划分。

CHARACTERISTICS OF GROUND MICROTREMORS OF THE CONSTRUCTIVE SITES OF TIANSHUI CITY

Through the observation and analysis of the ground mierotremors of Tianshui city,it is shown that there are many factors which influence the amplitude of microtremors.The amplitude of the microtremors changs wi-th the topographical and geomorphoiogical conditions.The horizontal mic-rotremors evidently appear to have a predominate direction,which is con-strained by the surrounding topography and geomorphdogy as a whole,and the effects Of the local site conditions on it is secondary.Some variations of the spectrum characteristic of the ground microtre-mors appear only in the large area,and the spectrum character is cons-trained by the situation of the area geology and new tectonic motion.The resulting spectrum characteristic of the microtremors are the superposi-tion of the effects of the local site conditions and the influences of the area background.The relationship between the characteristics of the ground microtre-mors and the strong earthquake ground motions is an important research theme on the study of field earthquake ground motion in future.According to the predominate period and aspect of the spectra of gro-und microtremors,We have divided Tianshui city into some microzones.