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

作者:: 王曰风¹; 2; 刁桂苓³; 张秀萍²; 张彦清²; 朱振兴²; 马利军²; (1.中国科学技术大学地球与空间科学学院,合肥 230026; 2.河北省地震局张家口中心台,河北张家口 075000; 3.河北省地震局,石家庄 050021)

Author(s):: WANG Yue-feng¹; 2; DIAO Gui-ling³; ZHANG Xiu-ping²; (1.School of Earth and Space Sciences,University of Science and Technology of China,Hefei 230026,Anhui,China)(2.Center Station of Zhangjiakou,Earthquake Administration of Hebei Province,Zhangjiakou 075000,Hebei,China)(3.Earthquake Administration of Hebei Province,Shijiazhuang 050021,Hebei,China)

Keywords:: aftershock sequence; focal mechanism; regional structural stress field; stress field in source area; Yongsheng of Yunnan

摘要:: 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。

Abstract:: We used maximum amplitude ratio of P_g- and S_g- 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.