小江断裂中段及邻区构造应力场分布特征
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摘要
本文利用小江断裂及邻区1998年1月～2007年9月发生的613个ML≥2.5地震的垂直向直达SV波和P波地动位移振幅比计算得出了这些地震的震源机制解;并根据区域构造对小江断裂中段及邻区现代构造应力场进行了分区。以小江断裂为界,将小江断裂中段及其邻区分为A、B(包含小江断裂带)两个区,为了研究断裂带上的应力特征,又将小江断裂带区域划分出来进行独立分析;同时采用网格1°×1°,以及0.5°空间滑动分区的办法进行研究。分析了该区震源机制解特征,并在此基础上利用应力张量反演方法,对研究区域的应力场进行反演。结果表明:①小江断裂中段及邻区的断层错动方式主要以走滑为主,A区、B区和断裂带区域走滑断层分别占81.28%、69.63%、72.97%。②A区的最大主应力σ1方位大致为NNW向,B区和断裂带区的最大主应力σ1方位大致为NWW向;从应力结构来看,应力以水平作用为主,走滑特征明显。③在整个滇中块体,应力场的主体方位由NNW向变为NWW向。但在元谋断裂以东,普渡河断裂以西的区域,主压应力方位表现出明显的南北向滑移,而在小江断裂区域主压应力则主要为NW向。从小江断裂继续往东的滇东块体上,应力场主压应力方位为NW-NNW向。
With 613 earthquake wave data of ML≥2. 5 in middle section of Xiaojiang fault and its adjacent area occurring from January 1998 to September 2007,all focal mechanisms are calculated with the direct wave amplitude ratio method of SV /P in vertical orientation,and their characteristics are analyzed. According to regional tectonic feature of middle section of Xiaojiang fault and its adjacent area,the research field is divided into two zones (A and B) along Xiaojiang fault ( the fault is included ) to make detailed study of the stress of Xiaojiang fault. An independent analysis is made on the Xiaojiang fault zone. 1° × 1° grids with 0. 5° slip trapeze zones are adopted in the study. The inversion of the stress fields in the zones with the method of FMSI shows that the fault's main strain-slip in middle section of Xiaojiang fault and its adjacent area is lateral,the A and B zones and the fault zone respectively have 81. 28% ,69. 23% and 72. 97% lateral fault. The stress inversion also indicated that the azimuth of maximum principal stress σ1 in A and B and the fault zone are respectively approximately NNW and NWW,the stress action is mainly horizontal,and strike-slip faulting is dominated in the study area. The 1° × 1° grids with 0. 5° slip trapeze in divided zone stress inversion shows that the direction change of principal stress field in central Yunnan block is NNW to NWW. However,in the region between Yuanmou fault and Pudu River fault,the azimuth of the main compressive stress shows that the North-South slip is obvious. While the azimuth of the main compressive stress of Xiaojiang fault zone is mainly NW,in the east of Xiaojiang fault,the direction of principal compressive stress about the eastern Yunnan block is NW to NNW.
With 613 earthquake wave data of ML≥2. 5 in middle section of Xiaojiang fault and its adjacent area occurring from January 1998 to September 2007,all focal mechanisms are calculated with the direct wave amplitude ratio method of SV /P in vertical orientation,and their characteristics are analyzed. According to regional tectonic feature of middle section of Xiaojiang fault and its adjacent area,the research field is divided into two zones (A and B) along Xiaojiang fault ( the fault is included ) to make detailed study of the stress of Xiaojiang fault. An independent analysis is made on the Xiaojiang fault zone. 1° × 1° grids with 0. 5° slip trapeze zones are adopted in the study. The inversion of the stress fields in the zones with the method of FMSI shows that the fault's main strain-slip in middle section of Xiaojiang fault and its adjacent area is lateral,the A and B zones and the fault zone respectively have 81. 28% ,69. 23% and 72. 97% lateral fault. The stress inversion also indicated that the azimuth of maximum principal stress σ1 in A and B and the fault zone are respectively approximately NNW and NWW,the stress action is mainly horizontal,and strike-slip faulting is dominated in the study area. The 1° × 1° grids with 0. 5° slip trapeze in divided zone stress inversion shows that the direction change of principal stress field in central Yunnan block is NNW to NWW. However,in the region between Yuanmou fault and Pudu River fault,the azimuth of the main compressive stress shows that the North-South slip is obvious. While the azimuth of the main compressive stress of Xiaojiang fault zone is mainly NW,in the east of Xiaojiang fault,the direction of principal compressive stress about the eastern Yunnan block is NW to NNW.
引文
程万正、刁桂苓、吕弋培等,2003,川滇地块的震源力学机制、运动速率和活动方式,地震地质,25(1),71～87。
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宋方敏、汪一鹏、俞维贤等,1998,小江活动断裂带,北京:地震出版社。
王绍晋、龙晓帆、余庆坤,2005,昆明地区现代构造应力场分析,地震研究,28(2),178～184。
谢富仁、苏刚、崔效锋,2001,滇西南地区现代构造应力场分析,地震学报,23(1),17～23。
许忠淮、汪素云、黄雨蕊,1987,由多个小震推断的青甘和川滇地区地壳应力场的方向特征,地球物理学报,30(5),476～486。
Gephart J.W.,1990,FMSI:A Fortran program for inverting fault/slickenside and earthquake focal mechanism data to obtain theregional stress tensor,,Computer&geoscience,16(7),953～989.
崔效锋、谢富仁、张红艳,2006,川滇地区现代构造应力场分区及动力学意义,地震学报,28(5),451～461。
阚荣举、张四昌、晏凤桐等,1977,我国西南地区现代构造应力场与现代构造活动特征的探讨,地球物理学报,20(2),96～109。
阚荣举,1980,西南地区现代构造应力场与板内强震活动,地震研究,3(3),45～59。
李坪、汪良谋,1977,云南川西地区地震地质基本特征的探讨,见:国家地震局西南烈度队编,西南地区地震地质及烈度区划探讨,北京:地震出版社。
宋方敏、汪一鹏、俞维贤等,1998,小江活动断裂带,北京:地震出版社。
王绍晋、龙晓帆、余庆坤,2005,昆明地区现代构造应力场分析,地震研究,28(2),178～184。
谢富仁、苏刚、崔效锋,2001,滇西南地区现代构造应力场分析,地震学报,23(1),17～23。
许忠淮、汪素云、黄雨蕊,1987,由多个小震推断的青甘和川滇地区地壳应力场的方向特征,地球物理学报,30(5),476～486。
Gephart J.W.,1990,FMSI:A Fortran program for inverting fault/slickenside and earthquake focal mechanism data to obtain theregional stress tensor,,Computer&geoscience,16(7),953～989.
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