2017年九寨沟地震序列南北分布不一致的成因分析  

Causes of the discordance in the south-north distribution of the 2017 Jiuzhaigou earthquake sequences

作　　者：靳志同[1,2,4] 刘佳璐 万永革 盛书中[3] 王福昌 张小涛 冯淦[1] Jin Zhi-Tong;Liu Jia-Lu;Wan Yong-Ge;Sheng Shu-Zhong;Wang Fu-Chang;Zhang Xiao-Tao;Feng Gan(Institute of Disaster Prevention,Sanhe 065201,China;Beijing Disaster Prevention Technology Co.,LTD,Beijing 101110,China;School of Geophysics and Measurement-control Technology,East China University of Technology,Nanchang 330013,China;Hebei Key Laboratory of Earthquake Dynamics,Sanhe 065201,China;Hongshan Seismological Observatory of Hebei Earthquake Agency,Xingtai 054000,China;Hebei Hongshan National Observatory on Thick Sediments and Seismic Hazards,Xingtai 054000,China.)

机构地区：[1]防灾科技学院,河北三河065201 [2]北京防灾科技公司,北京101100 [3]东华理工大学地球物理与测控技术学院,南昌330013 [4]河北省地震动力学重点实验室,河北三河065201 [5]河北省地震局红山基准台,河北邢台054000 [6]河北红山巨厚沉积与地震灾害国家野外科学观测研究站,河北邢台054000

出　　处：《Applied Geophysics》2023年第2期225-238,242,共15页应用地球物理（英文版）

基　　金：Funded by the National Natural Science Foundation of China(Nos.42174074,42364005,and 41704053);the Science and Technology Project of Hebei Education Department(No.ZD2022160);the East China University of Technology Research Foundation for Advanced Talents(ECUT)(No.DHBK2019084);the Fundamental Research Funds for the Central Universities(No.ZY20215117).

摘　　要：2017年九寨沟地震序列主震北部的余震分布较为分散,而主震南部的余震分布较为平直且集中。本研究基于地震震源机制的水平应变花、面应变和基于区域应变率的适应系数,分析上述不一致的动力学成因,得到以下结论:(1)主震北部具有震源机制的余震中约有三分之一为逆冲型地震,而且由于区域构造主压应变方向与主震北部断层走向垂直,确实也容易促使低倾角断层上逆冲型地震的发生,同时由于主震北部整体震源机制为逆冲型,以及主震北部的地震序列引起的断层运动与板块构造运动的一致性较差等原因,都导致主震北部余震较分散。(2)主震南部具有震源机制的余震中只有1个逆走滑型,但是有30个为走滑型地震,而且区域构造主压应变方向与主震南部断层走向的夹角较大,这使得主震南部断层更容易产生走滑型地震,同时主震南部整体震源机制为走滑型,以及主震南部的地震序列引起的断层运动与板块构造运动的一致性较好等原因,都使得主震南部余震较平直且集中。本研究结果对研究巴颜喀拉东北缘虎牙断裂隐伏断层的活动性及发震性质也有一定意义。In the 2017 Jiuzhaigou earthquake sequence,the distribution of aftershocks in the north of the main earthquake was scattered,while the distribution of aftershocks in the south of the main earthquake was linear and concentrated.The objective of this inquiry is to analyze the dynamic causes underlying such divergent patterns,relying on the horizontal strain rosette,areal strain(As),and the coefficient of accommodation(Ca)based on the regional strain rate.The following two conclusions are obtained:(1)approximately one-third of the aftershocks with focal mechanisms in the north of the main shock are thrust-type earthquakes.Because the direction of regional tectonic principal compressional strain is perpendicular to the fault trend north of the main shock,generating thrust-type earthquakes on low dip-angle faults is indeed easy.Simultaneously,the overall thrust-type focal mechanism north of the main shock and the poor consistency between plate tectonic movement and fault movement caused by the seismic sequence lead to substantial scattered aftershocks in the north of the main shock.(2)One of the aftershocks with focal mechanisms in the south of the main shock is a reverse strike-slip type,while the other 30 are strike-slip type earthquakes.Moreover,the angle between the regional tectonic principal compressional strain direction and the fault trend in the south of the main shock is large,which makes it easier for faults in the south of the main shock to produce strike-slip-type earthquakes.Simultaneously,the overall strike-slip focal mechanism in the south of the main shock,the good consistency between fault movements caused by the seismic sequence,and plate tectonic movements lead to more linear and concentrated aftershocks in the south of the main shock.The findings are significant for investigations into the seismogenic properties and activity of the Huya Fault located on the northeastern margin of Bayan Har Block.

关 键 词：九寨沟地震序列 应变花 面应变 应变率 适应 系数 

分 类 号：P315[天文地球—地震学]