1976年8月松潘地震强震与脉动频谱特性的分析

ANALYSIS OF THE CHARACTERISTICS OF SPECTRA OF THE STRONG GROUND MOTION AND MICROTREMORS-AUGUST 1976 SONGPAN EARTHQUAKE

摘要:

地面脉动与地震地面运动之间有没有关系?是什么关系?众说不一。1976年松潘地震记录提供了探讨这一问题的条件。我们对台址进行了各种工作之后,得出的结论是:(1)地震地面运动加速度和富氏谱峰值随震级而增大;脉动幅值及谱幅值随测点高程及地表沉积层厚度而加大。(2)同一地区脉动和不同序列地震记录的幅值及谱幅值的最大值,均有一定方向性。(3)同一序列地震谱曲线特征极为相似。(4)一层穿斗木架房屋结构对地面脉动频谱特性没有影响;而后者在前者的谱曲线上有明显反应。
结论:从1976年松潘地震文县台址的资料分析来看,地面脉动频谱特性在地震地面加速度谱形态或特征方面关系不明显。

Abstract:

Does any relation between microtremors and ground motion induced by the earthquake exist? And what is the relation like? There are different answers by different researches. The Songpan earthquake in 1976 supplied, the chance to discuss this problem. From the investigation we come to the following conclusions:(1)Both the acceleration and the maximum amplitude of Fourier spectrum of ground surface motion induced dy earthquake increase with the earthquake magnitude increasing; and both the amplitude of microtremors and its Fourier spectra increase with the altitude of observation site and the thickness of alluvial stratum increasing. (2) The amplitude of microtremors and the surface motion induced by different series of earthquake in the same site appears to have certain direction. (3)The characteristics of the Fourier spectra of the same series of earthquake are exactly alike. (4)The old style wooden house of one storey does not affect the spectrum of microtremors, but the site condition obviously affects the Fourier spectrum of the microtremors of the wooden house.
By these analyses it is concluded that there is no obvious relation between spectra of ground microtremors and ground surface motion induced by the earthquake.