2009年中国大陆地区部分地震的震源机制解

Focal Mechanism Solutions for Some Earthquakes in the Chinese Mainland in 2009

选用国家地震台网和区域台网的初至波P波初动符号资料,采用下半球等面积投影,用格点尝试法计算了2009年中国大陆27次MS4.5级以上地震的震源机制解。根据Zoback[1]研究全球应力场时的分类标准,对断层面解类型进行了分类。结果表明:走滑型(SS)地震13次,逆断层为主兼走滑(TS)8次,逆断层(TF)2次,正断层为主兼走滑(NS)3次,正断层(NF)1次。主压应力轴P轴方位的优势分布具有明显的区域特征,除东北地区有稍微的偏移,其余地区都与当地的背景构造应力场基本一致。

In this paper, the focal mechanism solutions of some earthquakes of Ms ≥4.5 occurring in the Chinese mainland in 2009 are determined with the lower hemisphere equal-area projection and first motion direction data of Pn and Ps waves recorded by the regional and distant seismic stations. In the calculation, the grid point test method is employed. The types of the focal fault plane are classified according to the classificatory criteria proposed by Zoback （1992） through the study of the global stress field. The results show that focal mechanism solutions of 13 earthquakes show strike-slip （SS） faulting, 8 are predominately thrust-faulting with strike-slip component （TS）, 2 thrust faulting （ TF）, 3 predominately normal faulting with strike-slip component （ NS）, and only 1 normal faulting （NF）. The predominant orientation of principal compressive stress P axis is different for different regions, and coincident with the local tectonic stress field, but the predominant orientation of P axis in the northeast of China deflected from the localtectonic stress field.