地震作用下山体地形地震动偏振效应研究  

Polarization effect on the ground motion of mountain topography under earthquake action

作　　者：王伟 齐亚坤 熊文 王浩宇 李金宇 张晓庆 Wang Wei;Qi Yakun;Xiong Wen;Wang Haoyu;Li Jinyu;Zhang Xiaoqing(School of Geological Engineering,Institute of Disaster Prevention,Hebei Sanhe 065201,China;Shanghai Earthquake Agency,Shanghai 200062,China;Shanghai Sheshan National Geophysical Observatory,Shanghai 200062,China)

机构地区：[1]防灾科技学院地质工程学院,河北三河065201 [2]上海市地震局,上海200062 [3]上海佘山地球物理国家野外科学观测研究站,上海200062

出　　处：《地震学报》2024年第4期695-708,共14页Acta Seismologica Sinica

基　　金：中央高校基本科研业务费研究生科技创新基金(ZY20220313);中国地震局地震科技星火计划(XH23062A);中央高校基本科研业务费(ZY20180107)共同资助.

摘　　要：基于汶川M_(S)8.0地震后在窦圌山坡顶和坡脚测点获得的9次余震记录,通过基线校正、滤波处理,得到各余震记录的傅里叶谱谱比及质点运动轨迹图,结果表明山体的自振频率具有多阶段性,其最大位移方位会出现在山体的横向或走向上,且山体存在偏振效应。将9次余震东西向和南北的水平向加速度时程以10°为单位进行分解得到324条新的时程曲线,基于分解合成后的时程记录,将坡顶与坡脚相同分解角度下的时程作比值,对其峰值加速度比和傅里叶谱谱比进行分析,结果表明二者最大值所在的方位均与山体最大位移所在的方位相同。结合9次余震坡脚测点的傅里叶谱分析可知,各输入地震动频率成分丰富的频段有所不同,低频段容易激发山体的低阶振型,导致山体在横向上发生偏振;高频段容易激发山体的高阶振型,导致山体在走向上发生偏振;当二者同时存在时,山体会同时产生低阶和高阶偏振效应。A large number of earthquake site investigation and theoretical studies have shown that local site conditions have a significant effect on seismic damage and ground motion characteristics,which is usually manifested as amplification or reduction of ground motion.The mountain topographic effect of strong ground motion plays a great role in the antiseismic defense of major projects in mountainous areas.Currently,there are three main ways to study the topographic effect:topographic effect observation array,analytical analysis and numerical simulation calculation.The strong motion observation data from the array can directly reflect the characteristics caused by the complex terrain,and analysis results are more intuitive,real and reliable.Based on the nine aftershock records after the 2008 Wenchuan MS8.0 earthquake,the baseline-correction and filtration were carried out,and the Fourier spectral ratios and particle motion displacement trajectory diagrams were achieved.The average spectral ratio curve of the two horizontal records of 9 aftershocks has good consistency with the spectral ratio curve of a single aftershock.The natural frequency of the mountain is not unique,and the maximum spectral ratio will appear in different frequency bands,indicating a clear multi-order nature of the mountain vibration.1.0-4.0 Hz is the lowerorder vibration mode of the mountain,and 9.0-15.0 Hz is the higher-order vibration mode.There are significant differences in the source,magnitude,epicenter distance,and propagation path of each aftershock,but the spectral ratio curves of each aftershock have good consistency,indicating that the natural frequency of the mountain is related to factors such as the geometric shape of the mountain itself.The particle motion displacement trajectory diagrams show that under different earthquake input,the maximum displacement amplitude of the mountain vibration can appear in the transverse or longitudinal direction of the mountain.There exists the obvious polarization effect in the mountain vibration.The

关 键 词：地震动 山体地形 偏振效应 谱比 加速度 

分 类 号：P315.9[天文地球—地震学]