2021年云南漾濞6.4级地震震源区地壳应力不均匀性研究  

STUDY ON HETEROGENEITY OF THE STRESS FIELD IN THE YANGBI EARTHQUAKE FAULT ZONE

作　　者：万永革[1,2,3] 王昱茹 靳志同 WAN Yong-ge;WANG Yu-ru;JIN Zhi-tong(Institute of Disaster Prevention,Sanhe 065201,China;Hebei Key Laboratory of Earthquake Dynamics,Sanhe 065201,China;Hebei Hongshan Thick Sediment and Earthquake Disaster National Field Scientific Observation and Research Station,Longyao 055350,China)

机构地区：[1]防灾科技学院,三河065201 [2]河北省地震动力学重点实验室,三河065201 [3]河北红山巨厚沉积与地震灾害国家野外科学观测研究站,隆尧055350

出　　处：《地震地质》2023年第4期1025-1040,共16页Seismology and Geology

基　　金：国家自然科学基金(42174074,41674055);河北省教育厅科学技术研究项目(ZD2022160);中央高校科研业务专项(ZY20215117);河北省地震动力学重点实验室开放基金(FZ212105)共同资助

摘　　要：精细地壳应力场在地球动力学研究中具有至关重要的作用。2021年云南漾濞地震序列发生在地震观测台站密集分布的地区,丰富的漾濞地震序列资料为该地区的精细应力场分析提供了大量地震震源机制解数据。为分析漾濞地震震源区的应力状态、断层构造和地震动力学关系,首先选择震源机制中心解算法对搜集到的漾濞地震序列震源机制解进行中心解求解,以保证震源机制数据的准确性;其次基于地震序列发生的位置,采用移动窗方法将震源机制解划分为6个区域,分别求解了6个区域的应力张量数据;最后分析了非均匀应力场所揭示的动力学问题。研究结果表明:漾濞地震震源区西北部和东南部的压应力轴方向由NNW-SSE向转换为NNE-SSW向,偏转角度达23°,且西北部的应力形因子大于东南部。推测西北部和东南部明显的应力场变化是由破裂区北部物质南移受阻和印缅弧深部NNE向低角度俯冲导致研究区浅部出现NNE向拉张联合作用所致。漾濞地震序列破裂东南区呈现马尾状散开的断层分布及山脉和水系走向在周围的分布均与本研究推测的应力偏转和应力形因子改变相符。这些研究对认识该地区的断裂活动特性和地震动力学具有一定意义。The fine crustal stress field plays an important role in geodynamics.The 2021 Yangbi earthquake sequence occurred in an area with densely deployed seismic stations.Before the mainshock,there occurred multiple 3-4 magnitude earthquakes.The mainshock was followed by strong aftershocks,MS5.0 and MS5.2,occurring 7 and 36 minutes later respectively.The earthquake sequence is a typical example of a“foreshock-mainshock-aftershock”earthquake sequence.The abundant seismic data of the 2021 Yangbi earthquake sequence provide many seismic focal mechanisms for the fine stress field analysis in the study region.To study the relationship of the stress field,fault structure,and earthquake dynamics in the Yangbi earthquake source region,the central focal mechanism solution algorithm is selected for the earthquakes with several focal mechanisms to ensure the accuracy of the focal mechanism data,and 93 precisely determined focal mechanism data are determined.The overall stress field in the source region is determined as a compressive stress axis of nearly NS direction and extensional stress axis of nearly EW direction.Then,to reveal the heterogeneity of the stress field in the source region,according to the location of the earthquake sequence,the focal mechanism solutions are divided into 6 regions by using the moving window strategy and obtain the stress field in each sub-region.To verify the inversion results are not caused by the selection of a specific partition mode,we used two different partition methods to discuss the stress field inversion experiments:1)change the number of sub-regions from 6 to 8,the number of focal mechanisms in each subregion is still 23,and moving the 15 focal mechanisms in each iteration;2)the number of the sub-region is still 6,change the number of focal mechanism to 28 in each subregion.It can be found that although the different partition strategies are changed,the characteristics of the obtained stress field will not change.Finally,the earthquake dynamics revealed in the heterogeneous stress ar

关 键 词：漾濞6.4级地震 震源机制解 应力场反演 不均匀性 断层结构 

分 类 号：P315.2[天文地球—地震学]