芦山地震强地面运动频谱特征及致灾相关性分析

以芦山地震震中距100km内20个台站的60条原始强震记录为依据,采用零交法计算台站处三方向卓越周期,采用线性加速法计算台站处阻尼比为0.05的三方向反应谱,考察反应谱峰值周期、卓越周期和放大系数在各台站位置处的分布以及在断裂上、下盘的均值。通过研究发现:芦山地震动卓越周期、反应谱峰值周期和放大系数在各台站不同方向上的分量不同;各台站处反应谱的计算表明地震动具有上盘效应以及上盘衰减迅速的特征;地震动卓越周期在芦山地震震中100km的上、下盘上差别不大,其中上盘EW和UD向卓越周期均值略小于下盘,而上盘NS向均值略大于下盘,断裂两盘UD向卓越周期总体小于水平向,断裂两盘三方向卓越周期变化范围为0.013~0.275s;计算得到的放大系数表明80%台站NS向放大系数大于EW向,因此NS向放大系数较大可能是芦山地震诱发崩滑地质灾害的主要因素。

Spectrum Characteristics of Strong Ground Motion during the Lushan Earthquake and Correlation Analysis of the Resulting Disaster

This work is based on 60 strong earthquake records from 20 stations within a distance of 100 km of the epicenter of the Lushan earthquake provided by the China Strong Motion Network Center (CSMNC).In this study,we applied zero-crossing and linear acceleration methods to calculate the predominant period and response spectra in three directions from the 20 stations with a damping ratio of 0.05.We then computed the distributions of the peak and predominant periods of the response spectra,the amplification coefficient in the computational region,and their mean values in the hanging wall and foot wall of the fault.Results showed that the peak and predominant periods of the response spectra and the amplification coefficients were different at all 20 stations.The response spectra showed the hanging wall effect and the characteristics of rapid ground motion decay in the hanging wall.Within 100 km of the epicenter,the predominant period was almost equal at both the hanging wall and foot wall.In fact,the mean value of the predominant period in the EW and UD directions in the hanging wall was slightly less than in the foot wall,and the mean value of the predominant period in the NS direction in the hanging wall was slightly larger than in the foot wall.In general,the predominant period in the UD direction was less than in the horizontal direction,and the range of the predominant period in all directions on both sides of the fault was 0.013~0.275 s.The amplification coefficient in the NS direction at 80 percent of the stations was larger than that in the EW direction;therefore,the larger amplification coefficient in the NS direction is possibly the main reason for the landslide during the Lushan earthquake.