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Title:: Characteristics of Wave-velocity Ratio,Focal Depth and Medium-small Seismicity before Strong Earthquakes in Yunnan

Author(s):: LI Yong-li; MAO Hui-ling; WANG Shi-qin; QIN Jia-zheng; (Earthquake Administration of Yunnan Province,Kunming 650224,Yunnan,China)

Keywords:: wave-velocity ratio; focal depth; medium-small earthquake; active period; Yunnan

摘要:: 分析了云南地区第四强震跃期内波速比的变化规律,探讨了强震孕育过程与波速变化、震源深度变化、中小地震活动的关系,结果表明:波速比异常、震源深度变化异常与3、4级中小地震活动的异常,最早出现于云南7级地震前4年左右,大多数异常集中出现于震前2年左右,表现为波速比、震源深度异常增多,震前1年左右异常则逐步减少; 伴随着云南第四强震活跃期的开始—结束的过程,云南地区的波速比也经历了下降—恢复的准同步过程。

Abstract:: We study the variation regularity of wave-velocity ratio in the 4th active period of strong earthquakes inYunnan,and discuss the relation between strong earthquake genesis and variation of wave velocity,medium-small earthquakes,and variation of focal depth.The result shows that wave-velocity ratio,focal depth and anomaly of M3-4.9 earthquakes appeared as early as 4 years before the M≥7.0 earthquakes.Most of them appeared about 2 years before the strong earthquakes,and anomaly of wave-velocity ratio and focal depth increased and gradually reduced about one year before the strong earthquakes.Corresponding to the beginning and the ending of the 4th active period.Wave-velocity ratio in Yunnan experienced the quasi-synchronous declining and rising.