内蒙古地区场地响应区域特征分析

本文以内蒙古地区台站分布、地质构造和地震活动性为基础,将内蒙古的大部地区划分为三个研究区域分别进行了场地响应研究。对近几年积累的大量ML≥3.0级以上地震,共计39个台站记录到的124次地震事件的785条波形,根据S波的观测振幅谱,采用遗传算法分别反演了三个区域的介质非弹性衰减系数和台站场地响应,并对其进行了讨论。本文得到的介质衰减模型和台站场地响应,将对台网测定ML震级需要考虑的量规函数、台站校正值等提供重要参考。研究结果表明:除个别台站存在场地放大或缩小的响应外,绝大多数台站的场地响应表现出一定的区域性特征;西部区域(除极个别台站外)对高频存在明显衰减;中东部区域对整个频段的反映都比较稳定;东部区域对整个频段存在明显放大,这与该区域覆盖层厚度大相吻合。

Regional Characteristic Analysis on Site Response of Digital Stations in Inner Mongolia

Inner Mongolia region is divided into three areas on the basis of seismic activity, station layout and geological tectonics, in which 785 waveform recordings of 124 earthquakes with ML equal or greater than 3.0 from 39 stations are processed in this study. We applied a lag-window spectral technique to obtain a stable Fourier spectrum of signals and noises. By adopting Genetic algorithm, reflected respectively transmission medium inelastic attenuation coefficient and station site response of three different tectonic regions are analyzed in order to obtain medium attenuation model and spectrum of station site response, which will be significant in providing important reference to earthquake magnitude corrected value of station. The results show that site response of most stations is of regional characteristics. In specific, high frequency shows strong attenuation for stations in western region; whereas no strong attenuation from stations in middle east region; remarkable enhancement of whole frequency arrangement from stations in eastern region. The above observation is in good agreement with the thickness variation of covering layer in the area.