新疆天山中段两次Ms6.0地震前异常特征的聚类分析

分别选取2011-11-01精河Ms6.0地震和2012-06-30新源-和静Ms6.6地震自2009-01以来100 km范围内ML3.0以上地震， 使用CAP和P波初动方法计算震源机制解，并对主震前震源机制解进行聚类分析。结果表明，震中附近震前半年左右，震区周围地震断层性质逐渐由紊乱变为统一；最大主压应力P轴方位由随机逐步呈现相对突出方向，且逐步与主震方向一致。

The Abnormal-Characteristics of Cluster Analysis before the Two Ms6.0 Earthquakes that Occurred in Middle of Mount Tianshan

We analyze the Ms6.0 earthquake in Jinghe on November 1, 2011 and the Ms 6.6 earthquake on the border of Xinyuan and Hejing on June 30, 2012. We identify earthquakes with magnitude greater than ML3.0 since Jan 2009, in a range of 100 km around these two earthquakes. We use CAP method and first motion direction about P-wave inverse the focal mechanism solution, then do a cluster analysis for these focal mechanism solutions. Our study shows that, about six months before the main-shock, the earthquakes’ fault nature changes from disorder to order; the maximum compressive principal stress P-axis azimuth changes from random to prominent, which is consistent with the direction of main-shock’s step by step.