【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Vavry■uk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。更多还原

【Abstract】 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 the Sichuan-Yunnan block. Overall,the characteristics of the source mechanism are consistent with the regional tectonic background.Results of the stress field inversion confirmed main active fault in the Eastern Boundary of the Sichuan-Yunnan Block is under a strike-slip stress regime,maximum and minimum compressional stress axes are nearly horizontal. The maximum compressional axes are primarily oriented in NW-SE and NWW-SEE direction,and they experience a clockwise rotation from north to south. Against the strike-slip background,normal faulting stress regimes and reverse faulting stress can be seen in the regional areas. The most prominent is the Daliangshan fault zone,which has obvious differences from the overall characteristics of the stress field with the eastern boundary of the Sichuan Yunnan Block.The maximum horizontal principal stress in the northern section shows a nearly EW direction,with a strike-slip type stress property,and the NW-SE direction in the southern section,with a thrust type stress property. The distribution characteristics of the stress field are consistent with the fault type of sinistral strike-slip and thrust on the eastern boundary of the Sichuan Yunnan block The shape ratio R-value varies significantly,the R-value in the Sanchakou area is relatively high,with obvious extrusion characteristics,the R-values of the Xianshuihe fault zone,Anninghe fault zone and Xiaojiang fault zone are all between 0. 25-0. 5,showing NE-SW compression and NW-SE tension,and the tensile stress may be much less than the compressive stress( strike-slip type). The R values of the northern segment of the Daliangshan fault zone,the southern segment of the Anninghe fault zone,and Zemuhe fault zone are all between 0.5-1,showing NW-SE compression and NE-SW tension,and the compressive stress is greater than the tensile stress. To sum up,the current stress characteristics of the eastern boundary of the Sichuan Yunnan rhombic block are shear strain and local compression or tension.There are different friction coefficients of the main faults in the study area: The Anninghe fault zone is 0. 60,the Xianshuihe and Zemuhe fault zones are 0. 80,the Xiaojiang fault zone is 0. 75 and northern and southern sections of the Daliangshan fault zone are 0. 65 and 0. 85. The friction coefficients of the Xianshuihe Fault,the southern section of the Daliangshan Fault,and the Zemuhe Fault are above 0. 75. The high friction coefficients of these fault zones may be because they are strike-slip faults,and the friction coefficients themselves are relatively high. The southern section of the Xiaojiang fault zone may be related to the development of fault gouges in the fault zone.更多还原