2001年云南永胜6．0级地震余震序列震源机制解与震源区应力场分析

Focal Mechanism Solution of the 2001 Yongsheng M6.0 Earthquake's Aftershock Sequence and Stress Field in the Source Area

利用垂直向的Pg和Sg波的最大振幅比计算方法,计算了2001年云南永胜6.0级地震余震序列的震源机制解。通过统计方法和系统聚类分析方法,结合余震序列的震中分布,对永胜6.0级地震的震源机制解和震源区应力场的特征进行了综合分析。结果表明:(1)所得发震断层为NWW向直立右旋走滑断层,与美国哈佛大学的主震CMT解的节面一致,也与余震分布一致,证明结果比较可靠;(2)震区主压应力场方向为NNW—SSE,与其现今区域构造应力场主压应力方向(NNW向)一致,表明余震的应力场主要受主震震源应力场的控制。

We used maximum amplitude ratio of Pg- and Sg- wave to calculate the focal mechanism solutions of the 2001 Yongsheng, Yunnan, M6.0 earthquake＇s aftershock sequence. Combining with the epicenter distribution of the aftershock sequence, we comprehensively analyzed the solutions and the stress field in the source area by statistical method and systematic clustering procedure. The result shows： （ 1 ） The causative fault is NWW-direction upright right-lateral strike-slip fault, consistent with the plane of CMT solution from Harvard University, and with the distribution of the aftershocks, which indicates the credibility of the result. （2） The principal compression stress field is in NNW - SSE, with the same direction as the principal compression stress of present regional tectonic stress field in the source area, which indicates that the stress field of the aftershocks is controlled by the one of the mainshock.