摘要
通过对华北地区 196 3～ 1998年间 12 6个地震 (MS≥ 4 7)震源机制解的逐一筛选 ,运用逐次收敛法对中国华北地区现代构造应力场进行了反演分析 ,发现该地区现代构造应力场的方向在时间和空间上存在着较为明显的演变特征 :①中等主应力σ2 基本上是近垂直的 ,最大主应力σ1和最小主应力σ3 都接近水平 ,σ1、σ3 的方位在时间和空间上则存在着一定的变化 ;②1976年唐山地震以前 ,该地区现代构造应力场的方向基本一致 ,最大主应力σ1的方位角为 6 8°(北东东向 ) ;③ 1976年唐山地震以后 ,华北地区现代构造应力场的方向发生了一定的变化 ,华北北部地区和郯庐断裂带以东地区现代构造应力场的方向没有明显改变 ,最大主应力σ1的方向仍为北东东向 ,方位角保持 6 8°不变 ,而华北中南部地区最大主应力σ1的方位则发生了顺时针的转动 ,方位角变为 87°(近东西向 )。
By 126 earthquake focal mechanism solutions ( M S≥ 4 7) in the period of 1963～1998,the state of present tectonic stress field in North China is inversed by using the method of step by step convergence. The inv ersion results indicate that the stress field in the research area is clearly va riational in space and time:① The middling principal stress axis σ 2 is b asically vertical in North China. The maximum and minimum principal stress, σ 1 and σ 3 are nearly horizontal,but the azimuths of σ 1 and σ 3 are inequable in different districts and period. ② Before the Tangshan ea rthq uake in 1976,the three principal stress are uniform in North China. The azimuth of maximum principal stress axis σ 1 is 68°(striking in a NEE-SWW direc tion). ③After the Tangshan earthquake,the maximum principal stress axis σ 1 and minimum principal stress axis σ 3 are variational in different districts. In the northern and eastern areas of North China,the maximum princip al stress axis σ 1 is also striking in a NEE-SWW direction,and the azimut h is 68° that is same as before the Tangshan earthquake. In the southe rn a rea of North China,the maximum principal stress axis σ 1 is striking in a E-W direction,and the azimuth is 87°.
出处
《中国地震》
CSCD
北大核心
2001年第3期280-288,共9页
Earthquake Research in China
基金
国家重点基础研究发展规划"大陆强震机理与预测"项目 (95 130 10 1)
地震科学联合基金 (1990 2 2 )资助课题
