安宁河—则木河断裂带及邻区中上地壳各向异性及其含义  

Anisotropy of middle-upper crust in the Anninghe-Zemuhe fault zone and its adjacent area and its implications

作　　者：刘庚[1] 吴晶[2] 周聪[1] 倪泰山 魏梦怡 王松[4] LIU Geng;WU Jing;ZHOU Cong;NI TaiShan;WEI MengYi;WANG Song(Second Crust Monitoring and Application Center,China Earthquake Administration,Xi'an 710054,China;Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;Earthquake Agency of Honghe Prefecture,Mengzi Yunnan 661199,China;Chengdu Earthquake Monitoring Center Station of Sichuan Earthquake Agency,Chengdu 611730,China)

机构地区：[1]中国地震局第二监测中心,西安710054 [2]中国科学院地质与地球物理研究所,北京100029 [3]云南省红河州地震局,云南蒙自661199 [4]四川省地震局成都地震监测中心站,成都611730

出　　处：《地球物理学报》2023年第11期4533-4551,共19页Chinese Journal of Geophysics

基　　金：国家重点研发计划(2017YFC1500503);国家自然科学基金(41904063);岩石圈演化国家重点实验室自主研究课题(SKL-Z202204);国家野外科学观测研究站项目(NORSTY2022-06);陕西省自然科学基础研究计划(2023-JC-QN-0337)共同资助。

摘　　要：本文采用剪切波分裂分析方法,使用安宁河—则木河断裂带及邻区的42个流动和固定地震台站2013年1月到2019年12月的近震波形记录,获得了各个台站的剪切波分裂参数结果.由于区域主压应力场以及局部地质构造的影响,该区快波偏振方向的空间分布具有明显的分区特征:以冕宁为界,安宁河北段石棉—冕宁段周边表现出NW-SE快波优势偏振方向,与华南地块主压应力方向一致,表明区域应力场对中上地壳各向异性起主要约束作用;安宁河南段冕宁—西昌段周边表现出差异性的局部快波优势偏振方向,为NE-SW,与其他区域明显不同,揭示了该区具有局部构造特征和应力环境;则木河断裂带北段快波优势偏振方向与安宁河北段优势偏振方向一致,为NW-SE向,表明区域最大主压应力方向的优势作用.安宁河北段的石棉—冕宁段附近台站,在康定MS6.4和石棉MS4.5地震前后,快波偏振方向均有变化,暗示中上地壳各向异性特征受到地震应力积累与释放过程的影响.此外,位于安宁河断裂和则木河断裂交界处的西昌地区(XC27台),既是构造交汇区,也是各向异性特征分段的边界,具有最大的慢波时间延迟,说明该区构造复杂、各向异性程度最强,值得关注;木里县(MLI台)、普格县(PGE台)、鲜水河断裂和龙门山断裂交汇处(HCP台)以及美姑县(XC36台)均具有较高的慢波时间延迟,且快波偏振方向与周围台站不同,考虑到这些台站位于断裂带交汇或分段的端部,亦是值得关注的地方.In this study,the polarization of fast shear-waves(PFS)and time delay of slow shear-wave beneath 42 stations(including fixed seismic stations and mobile seismic stations)in/around Anninghe-Zemuhe fault zone were calculated by shear-wave Splitting Analysis Method(SAM)based on the seismic data(Jan.2013—Dec.2019).Because of the impacts from both regional principal compressive stress and local geological structures,the parameters of PFS show obviously local characters.The Anninghe fault zone is bounded by Mianning.In the north of Anninghe fault Shimian-Mianning section,the PFS is in NW-SE direction,which agrees with the direction of principal compressive stress in Southern China,meaning that the anisotropy in the middle-upper crust is mainly dominant by the regional stress field.In the south of Anninghe fault Mianning-Xichang section,the dominant direction of PFS is NE-SW,which is different from that in other regions,showing the complicated characteristics of crustal structure and stress distribution under the interaction between sub-blocks.The dominant direction of PFS in the north section of Zemuhe fault zone is consistent with that in the north section of Anninghe fault zone,which is NW-SE,indicating the influence from the maximum principal compressive stress in the region.Before and after the Kangding MS6.4 and Shimian MS4.5 mainshocks,the direction of PFS in/around this area varies,suggesting that the anisotropy of the middle and upper crust is related to the accumulation and release of seismic stress.Xichang area(near XC27 station),at the junction of Anninghe fault and Zemuhe fault,is both a structural intersection and anisotropic inconsistence,with the largest time delay,meaning that this area has complex structure and the strongest anisotropy.In addition,Muli County(MLI station),Puge County(PGE station),the intersection area of Xianshuihe fault and Longmenshan fault(HCP station)and Meigu County(XC36 station),these stations show high time delay and various polarizations compared with the surrounding stations

关 键 词：安宁河-则木河断裂带 地壳各向异性 剪切波分裂 主压应力 

分 类 号：P315[天文地球—地震学]