基于相对震源机制解反演方法的广东及邻区区域应力场研究  

Regional stress field throughout Guangdong and its nearby areas revealed from relative focal mechanism inversion

作　　者：况文欢 张捷[4] 叶秀薇[5] 张伟 KUANG WenHuan;ZHANG Jie;YE XiuWei;ZHANG Wei(College of Marine Geosciences,Key Lab of Submarine Geosciences and Prospecting Techniques,Ministry of Education Ocean University of China,Qingdao Shandong 266100,China;Department of Earth and Space Sciences,Southern University of Science and Technology,Shenzhen Guangdong 518055,China;Guangdong Provincial Key Laboratory of Geophysical High-resolution Imaging Technology,Southern University of Science and Technology,Shenzhen Guangdong 518055,China;Department of Geophysics,University of Science and Technology of China,Hefei 230026,China;Guangdong Earthquake Agency,Guangzhou 510070,China)

机构地区：[1]中国海洋大学海洋地球科学学院,海底科学与探测技术教育部重点实验室,山东青岛266100 [2]南方科技大学地球与空间科学系,广东深圳518055 [3]广东省地球物理高精度成像技术重点实验室(南方科技大学),广东深圳518055 [4]中国科学技术大学地球物理系,合肥230026 [5]广东省地震局,广州510070

出　　处：《地球物理学报》2025年第4期1258-1270,共13页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(U1901602和42104047);国家重点研发计划(2021YFC3000703-05);广东省地球物理高精度成像技术重点实验室(2022B1212010002);广东省重大人才工程引进类(2019QN01G801)资助。

摘　　要：震源机制解描述地震断层的相对错动,在刻画断层空间取向、考察地应力分布等方面具有重要意义.目前,对于中强地震(M≥4.5),反演震源机制解的方法较为成熟,一般通过拟合观测数据和理论数据之间的初动极性、最大振幅(比)或波形信息进行反演,已经成为地震监测的日常工作之一.然而,对于数量众多的中小地震(M<4.5),由于其低频成分不发育、高频成分受限于速度模型难以准确模拟等原因,反演结果可能存在较大误差.为了更好的理解广东及邻区的应力场分布,本文先基于GCAP方法反演了该地区的几个较大地震事件;然后,应用一种基于主事件的震源机制解相对反演方法得到了该地区77个中小地震的震源机制解.在此基础上,综合利用已有研究和本文得到的震源机制解,采用迭代应力反演方法,分区反演了广东及邻区的应力场分布.结果显示,广东及邻区的应力场以走滑型为主,最大水平主应力方向大致为WNW,与前人结果基本一致.分区域看,粤桂交界和广东阳江地区的最大水平主应力方向约为西偏北40°和45°,而广东河源和珠江三角洲地区的最大水平主应力方向约为西偏北30°和22.5°.同时,地震断层的错动方式呈现出规律性的空间变化:从粤桂交界向东南方向,经过广东阳江和河源,到珠江三角洲,地震断层的错动方式呈现出从以正断为主兼具走滑、到以走滑为主兼具正断、再到接近纯走滑的规律性空间变化.考虑到粤桂交界地区山地褶皱构造较多,而珠江三角洲地区地质构造较为平缓,推测广东及邻区的构造应力状态可能与局部的地质构造复杂程度密切相关.本文的研究结果有助于加深对广东及邻区应力场的理解.Earthquake focal mechanism,which describes the dislocation of geological fault,is very important for characterizing the fault orientation and the stress field.Currently,for moderate-to-large earthquakes(M≥4.5),the method of inverting focal mechanism is well established by fitting the first-motion polarity,maximum amplitude(ratio),or waveform information between the observed and theoretical data and it has become one of the routine tasks in earthquake monitoring.However,for a large number of small-to-moderate earthquakes(M<4.5),due to the difficulties in modelling the high-frequency information in the waveforms,the inverted focal mechanisms may have large errors.In order to better understand the stress field in Guangdong and its nearby areas,we first invert the focal mechanisms of several larger earthquakes based on the widely used GCAP method;then,we perform a relative focal mechanism inversion to obtain the focal mechanisms of 77 small-tomoderate earthquakes.By jointly utilizing the focal mechanisms from both previous study and this study,the stress field in Guangdong and its nearby areas are inverted using an iterative stress inversion method.Results show that Guangdong and its nearby areas are predominantly strike-slip,and the orientation of the maximum horizontal principal stress is about WNW,which is consistent with existing studies.The maximum horizontal principal stress orientations in Guangdong-Guizhou junction and Yangjiang are about W40°N and W45°N,respectively.The maximum horizontal principal stress orientations in Heyuan and Zhujiang Delta are about W30°N and W22.5°N,respectively.Meanwhile,the source dislocation modes show regular spatial variations:from the Guangdong-Guizhou junction,to Yangjiang and Heyuan,and to the Zhujiang Delta,the source dislocation modes change from predominantly normal faulting with strike-slip,to predominantly strike-slip with normal faulting,and to nearly pure strike-slip.Considering that Guangdong-Guizhou junction presents complex geological structures and the Zhujia

关 键 词：震源机制解相对反演 中小地震 广东及邻区 区域应力场 

分 类 号：P315[天文地球—地震学]