伽师强震系列应力场的转向过程

A deflection process for the stress field of the Jiashi strong earthquake sequence

自1997～2003年,新疆伽师地区相继发生多次强震.取哈佛大学公布的伽师强震系列CMT(矩心矩张量解)解资料,由滑动矢量拟合法反演区域应力场.CMT解的系统聚类分析表现出3个阶段的时序特征.分析震源区应力场发现,1997年3月1日至2003年1月4日期间新疆伽师地区的应力场发生变化,2003年2月24日起,又恢复到基本应力场的方向,从而完成从基本应力场-变化应力场-基本应力场一次完整变动过程.结合区域受力状况和构造背景,讨论了新疆伽师强震系列应力场变化的成因,并且认为伽师强震系列具有体破裂的特征.

The Central Moment Tensor （CMT） solutions of Jiashi strong earthquake sequence issued by Harvard University are used to inverse the regional stress field. The systematic cluster analysis of the CMT solutions shows the time-sequence features of three periods. Further analysis of the stress field for the focal region indicates that the variations took place in the period from March 1, 1997 to Jan. 4, 2003. Since Feb. 24, 2003, the direction of basic stress field was recovered. Thus a complete process from the initial variation of the basic stress field to the final recovery of the basic stress field finished. Combining the stressed conditions and tectonic background of the region, the genesis for the stress field variation of the strong earthquake sequence is discussed. We suggest that the Jiashi strong earthquake sequence has the characteristics of body fracture.