云南地区震源机制及应力场特征  

CHARACTERISTICS OF FOCAL MECHANISMS AND STRESS FIELD OF YUNNAN AREA

作　　者：孙业君[1] 赵小艳[2] 黄耘[1] 杨浩[1] 李锋[1] 

机构地区：[1]江苏省地震局,南京210014 [2]云南省地震局,昆明650041

出　　处：《地震地质》2017年第2期390-407,共18页Seismology and Geology

基　　金：江苏省科技支撑-社会发展项目(BE2016804;BE2011814);中国地震局地震科技星火计划项目(XH15020Y);中国地震局震情跟踪青年课题项目(2016010121);江苏省地震局青年基金重点项目(201402)共同资助

摘　　要：利用云南和四川区域台网记录的地震波形资料,采用CAP方法计算得到了云南地区1999年1月至2014年8月268次M_L≥4.0地震的震源机制解,结合收集的哈佛大学1976年以来109次地震的震源机制解,分析了云南地区震源机制解分类及其区域特征。基于上述震源机制解资料,采用区域应力张量阻尼反演方法计算了云南地区每个网格的最佳拟合构造应力张量,并利用最大主应力计算方法计算得到了云南地区最大水平主应力的方向。结果表明:1)研究区地震震源类型以走滑型为主,其次为正断型,逆断型相对较少,震源机制空间分布特征明显,反映了研究区不同区域受力源及其作用方式的差异性;2)云南地区应力场方向呈现一定的空间连续性,最大水平主压应力方向由北向南呈顺时针旋转,由西向东呈逆时针旋转,同时应力场方向表现出空间的不均匀性,EW和SN方向分别存在2个应力转换区。应力场反演结果显示,云南地区应力场较为复杂,主应力方向变化很大,不同区域存在明显差异。Using the seismic waveform data recorded by regional seismic network of Yunnan and Sichuan and the method of CAP, we calculate and obtain the focal mechanism of 268 earthquakes with the magnitude of ML ≥ 4.0 occurring in Yunnan during Jan. 1999 to Aug. 2014; then, we analyze the types and the regional feature of the focal mechanism of earthquakes in Yunnan, on the basis of the focal mechanism of 109 earthquakes analyzed by Harvard University. Based on the data of the above focal mechanism solutions, we adopt the method of damped regional-scale stress inversion to calculate the best-fitting tectonic stress tensor of every grid in Yunnan; and adopt the method of maximum principal stress to calculate the direction of maximum horizontal principal stress in Yunnan. The result shows that ： （ 1 ） the strike-slip type is the most principal type of the earthquake focus in the study area and the second is the normal faulting type; while, the reverse-fault type is relatively small. The spatial distribution of focal mechanism is obvious. This reflects that the dynamic source and acting force are different in different parts of the study area. （2） The direction of the stress field in Yunnan shows a certain spatial continuity. Maximum horizontal principal compressive stress is mainly clockwise from north to south and counterclockwise from the west to the east. The direction of stress field shows inhomogeneity in space. There exist two stress conversion zones respectively in EW and NS direction. The inversion result of stress field shows that the stress field in Yunnan is complex and the principal stress direction changes greatly; and there are obvious differences in different regions.

关 键 词：震源机制解 CAP方法 应力张量阻尼反演 应力场 云南地区 

分 类 号：P315.727[天文地球—地震学]