方向性效应对2022年四川泸定MS6.8地震主余震长周期地震动的影响  

Directivity effect on long-period ground motion of the MS6.8 earthquake and its aftershock in Luding,Sichuan on 2022

作　　者：张峻杰 马强[1,2,3] 解全才 林德昕[1,2,3] 陶冬旺 ZHANG JunJie;MA Qiang;XIE QuanCai;LIN DeXin;TAO DongWang(Institute of Engineering Mechanics,China Earthquake Administration,Harbin 150080,China;Key Laboratory of Earthquake Engineering and Engineering Vibration,China Earthquake Administration,Harbin 150080,China;Key Laboratory of Earthquake Disaster Mitigation,Ministry of Emergency Management,Harbin 150080,China)

机构地区：[1]中国地震局工程力学研究所,哈尔滨150080 [2]中国地震局地震工程与工程振动重点实验室,哈尔滨150080 [3]地震灾害防治应急管理部重点实验室,哈尔滨150080

出　　处：《地球物理学报》2024年第7期2683-2696,共14页Chinese Journal of Geophysics

基　　金：黑龙江省自然科学基金项目(LH2022E119);中国地震局工程力学研究所基本科研业务费专项(2021B08)资助。

摘　　要：2022年四川泸定MS6.8地震主震是一次较为典型的近垂直断层走滑型地震,为研究地震动强度的方向性效应,本文利用震中距100km范围内121台强震仪和地震烈度仪的加速度记录,与中国西南地区衰减模型的预测结果进行了对比,利用谱加速度残差的分布对长周期地震动进行了分析,并与两次震源机制不同的余震进行了对比.结果表明:泸定主震的方向性效应明显,在周期T=1.5~3 s,东南向的向前放大效应显著;在周期T=0.5~1.5 s,西北向的向后方向削弱效应显著;方向性效应在倾滑型的余震中没有明显体现;不同走滑型地震的方向性效应在不同周期体现不同,泸定主震在T=0.5~4 s的方向性效应较其他长周期段更大,对比2022年的马尔康系列地震和2016年日本熊本地震,前者分别集中在T=2 s和3~6 s,后者方向效应随周期增大而增大.The seismogenic fault of Luding MS6.8 earthquake is characterized as a typical strike-slip fault,exhibiting a large dip angle and a relatively small rake angle.To study the directivity effect caused by this earthquake,this paper compared the acceleration time-history records obtained by 121 strong-motion stations located within 100 kilometers from the epicenter with the prediction results based on the attenuation model generated from historical earthquakes in southwest China.The analysis of distribution of the residual error was conducted on the long periods of acceleration response spectra,and a comparison was made between the mainshock and aftershocks with two completely different source mechanisms.The results indicate that:(1)The directivity effect of the Luding mainshock is obvious,which is reflected particularly in the periods of T=1.5~3 s,where the forward amplification effect is significant in the southeast direction.In the period range of T=0.5 s to 1.5 s,the backward attenuation effect in the northwest direction is significant,which is consistent with the directional mechanism caused by the rupture.(2)The directional effect is not obvious in the aftershocks,which are reverse faults.(3)The directivity effect of different strike-slip earthquakes is manifested differently at different periods.The amplification effect of this Luding mainshock at periods of T=0.5~4 s is greater than that of others.In contrast,the 2022 Markam's earthquakes sequence and the 2016 Kumamoto earthquake in Japan show different results.The former is concentrated in the range of T=2 s and 3~6 s,while the directivity effect of the latter increases with the increase of the period.

关 键 词：震源机制 长周期特性 方向性效应 泸定地震 

分 类 号：P315[天文地球—地震学] P223[天文地球—固体地球物理学]