2003年伽师6.8级地震序列特征和震源机制的初步研究

Preliminary Study on Characteristics of the Jiashi Earthquake Sequence with M_S 6.8 and Its Focal Mechanism Solation in 2003

在位于 1997～ 1998年新疆伽师 9次 6级地震分布区域的东南端 ,2 0 0 3年 2月 2 4日又发生 6 8级地震。结合伽师 6 8级地震序列震源机制解结果 ,对该地震序列的基本特征和震源区应力降等进行了对比分析。结果表明 ,6 8级地震断层是在北西向的区域应力场挤压作用下产生的倾滑逆断层 ,震源以单侧破裂为主 ,破裂方向与极震区走向 ,以及北西向的主压应力方向一致。震前震源区应力显著增强 ,震后应力释放较为彻底。中强余震震源机制解与主震有明显差异 ,表现出震源区应力场处于不稳定的调整阶段 ,余震震源机制的差异为震后地震趋势的判定提供了依据。

There occurred an earthquake with M S6.8 on Feb.24,2003 again at the southeastern end of the Jiashi region where occurred 9 events with M S6 from 1997 to 1998, Xinjiang. With focal mechanism solutions of the Jiashi earthquake sequence with M S6.8, we made contrastive analysis on basic feature of the sequence and stress drop in source region, etc. The result shows that fault type of M S6.8 earthquake is dip-slip thrust fault resulting from compression of regional stress field in an NW direction. Source rupture is one-sided mainly, and rupture direction is consistent with the strike of meizoseismal area and the direction of NW principal compressive stress. Stress in source region before the event increased obviously and released thoroughly after the event. There is clear difference between of moderately strong aftershocks and mainshock, which shows stress field in source region is in the phase of unstable adjustment. The difference of focal mechanism solution of aftershock offer criterion for postearthquake trend judgement.