川滇菱形块体东边界震源机制与应力场特征  

CHARACTERISTICS OF FOCAL MECHANISM AND STRESS FIELD IN THE EASTERN BOUNDARY OF THE SICHUAN-YUNNAN BLOCK

作　　者：郭祥云[1] 房立华[1] 韩立波[1] 李振月 李春来[1] 苏珊 GUO Xiang-yun;FANG Li-hua;HAN Li-bo;LI Zhen-yue;LI Chun-lai;SU Shan(Institute of Geophysics,China Earthquake Administration,Beijing 100081,China;Guangxi Earthquake Administration,Nanning 530000,China)

机构地区：[1]中国地震局地球物理研究所,北京100081 [2]广西壮族自治区地震局,南宁530000

出　　处：《地震地质》2024年第2期371-396,共26页Seismology and Geology

基　　金：国家重点研发计划项目(2017YFC1500501);地震科学联合基金(U2139205);中国地震局地球物理研究所基本科研业务专项(DQJB22Z04)共同资助。

摘　　要：文中利用四川、云南、重庆、青海、甘肃地震台网以及西昌密集台阵和巧家密集台阵的数字地震波形资料,采用CAP全波形反演方法及HASH初动极性和振幅比方法,获得了川滇菱形块体东边界区域3 951组M L≥1.0地震的震源机制。进而基于以上震源机制,采用阻尼区域应力场反演算法(MSTASI)和Vavrycuk的迭代联合反演方法获得了研究区的构造应力场分布特征、主要活动断裂的应力性质和摩擦系数。结果显示,研究区震源机制P轴、T轴以及最大主应力轴σ1和最小主应力轴σ3总体上倾角较小,揭示了近水平的挤压或剪切应力环境。σ1以NW-SE和NWW-SEE向为主,从北到南有顺时针旋转的趋势,应力性质以走滑型为主,局部兼有逆冲型和拉张型,整体分布特征与区内走滑型边界断裂活动性质一致。R值具有明显的空间差异,鲜水河断裂-龙门山断裂-安宁河断裂交会地区R值相对较高,有明显的挤压特征;鲜水河断裂带、安宁河断裂带北段和小江断裂带的R值均在0.25~0.5之间,表现为NE-SW向挤压和NW-SE向拉张,拉张应力可能远小于挤压应力;大凉山断裂带北段和则木河断裂带的R值均在0.5~1之间,表现为NW-SE向压缩和NE-SW向拉张,且挤压应力大于拉张应力。研究区域主要断裂的摩擦系数也有差异:安宁河断裂带和大凉山断裂带北段的摩擦系数相对较低,在0.75以下,鲜水河断裂带、则木河断裂带及大凉山断裂带南段的摩擦系数偏高,在0.80以上。川滇菱形块体东边界活动断裂带上的构造应力相对较高,尤其是鲜水河断裂带和小江断裂带的应力更高,需要关注其地震危险性。It is important to study the characteristics of the tectonic stress field studies which could provide a deeper understanding of the internal stress environment of the crust.It can provide useful assistance for exploring the relationship between the tectonic stress field and earthquake development.At the same time,it plays an important role in understanding block interactions,fault movement,tectonic deformation,and revealing the dynamic mechanical processes of the continent.The focal mechanism solutions contain abundant information reflecting the stress field.In this paper,using the broadband records from 128 permanent and temporary regional stations from the Chinese National Seismic Network(CNSN)deployed in the Sichuan-Yunnan Province and its adjacent,we determined the focal mechanisms of 3 951 earthquakes by the cut-and-paste(CAP)method and the HASH method.The friction coefficient and stress properties of the main active fault and characteristics of the tectonic stress field in this area are analyzed by using two different methods which are the damped inversion method(STASI)and iterative joint inversion method from focal mechanisms.The results of the focal mechanisms show that:there are 2 512 strike-slip earthquakes in the study area,accounting for 63.58%of all earthquakes;there are 818 normal fault type and normal strike-slip type earthquakes,accounting for 20.70%of all earthquakes;there are 621 reverse strike slip and reverse thrust earthquakes,accounting for 15.72%of all earthquakes.The most of earthquakes in the study area are distributed in active fault zones,the strike of the fault plane is consistent with the orientation of active fault zones.It revealed predominantly strike-slip faulting characteristics of earthquakes in the Eastern Boundary of the Sichuan-Yunnan Block,while the reverse thrust of earthquakes is mainly concentrated in the Longmenshan fault zone,as well as the NW trending Mabian-Yanjin Fault and the NE trending of Ludian-Zhaotong and Lianfeng faults which lied on the eastern boundary of th

关 键 词：川滇菱形块体东边界 震源机制 区域应力场 主压应力轴 摩擦系数 

分 类 号：P315.2[天文地球—地震学]