2022年9月5日四川泸定6.8级地震强震记录及典型强震动站点特征分析

Strong motion records from the Luding M 6.8 earthquake in Sichuan Province on September 5,2022,and characteristics of typical strong motion stations

对2022年9月5日四川泸定M 6.8地震中获取的205条强震动观测记录进行计算处理,发现近场站点NS向的地震动参数高于EW向,呈现出显著的方向性差异;根据计算的地震动参数结果,绘制峰值加速度(PGA)及峰值速度(PGV)等值线分布图,并研究该地震的衰减规律;计算近场站点的加速度反应谱峰值周期、90%重要持时及卓越周期,得出近场站点90%重要持时变化范围为10~30 s、平均持时为20 s;分析台站51LDJ及51LDL的加速度反应谱、傅里叶谱谱比,发现在不同震级、类似震中距的情况下,同一台站谱形主要受震源影响,震级越大,反应谱衰减越慢;计算分析M 6.8主震及余震中典型台站的水平与竖向速度反应谱谱比,51LDL台在主余震中卓越频率平移不明显,而51LDJ台在强震下出现卓越频率向低频(大周期)的大幅度移动,可能是站点的场地非线性反应引起。

A total of 205 strong motion records from the Luding M 6.8 earthquake in Sichuan Province on September 5,2022,were processed and analyzed.According to the calculated ground motion parameters,contour maps of peak acceleration and peak velocity were created,and the attenuation law of the M 6.8 earthquake was examined.The analysis revealed that the ground motion parameters in the NS direction were larger than those in the EW direction,indicating a significant directional difference.The peak period,90%important duration,and predominant period of the acceleration response spectrum at near-field stations were calculated.The 90%important duration ranged from 10 to 30 s,with an average duration of 20 s.The acceleration response spectrum and Fourier spectrum ratio for the typical stations 51LDJ and 51LDL were analyzed.The results indicate that,for different magnitudes and similar epicentral distances,the spectral shape is mainly influenced by the source.Specifically,as the magnitude increases,the response spectrum exhibits slower attenuation.The ratio of the vertical and horizontal acceleration response spectra for the two stations during the M 6.8 main shock and its aftershocks was calculated.The predominant frequency shift at the 51LDL station was not significant,while the predominant frequency at the 51LDJ station exhibited a notable shift to lower frequencies(longer periods)during the strong earthquake,which may be attributed to the nonlinear response of the site.