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Title:: Overview of Tracking of Qinghai Menyuan M_S6.4 Earthquake in 2016 and its Post Earthquake Precursor Anomaly Summary

Author(s):: TU Hongwei; WANG Peilin; ZHANG Xiaoqing; MA Zhen; HUANG Hao; Earthquake Administration of Qinghai Province,Xining 810001,Qinghai,China

Keywords:: Menyuan M_S6.4 earthquake; precursor anomaly; earthquake tracking

摘要:: 对2016年1月21日门源6.4级地震相关跟踪分析进行了回顾性总结,震前提取的背景性异常为自2010年4月14日玉树7.1级地震后69个月的6级地震平静、祁连地震带的3级地震低频次异常、低b值、高GL值、震源机制解一致性、跨断层形变等,而震前确认的前兆异常仅为2015年12月19日距震中约140 km的乐都气氡观测值出现大幅度下降变化; 震后总结时,通过资料收集,省内提取了平安静水位、湟源钻孔形变2项疑似异常,在甘肃省地震局收集到了7项中期前兆异常,但震中距都比较远。综合分析认为,在现今的观测过程中,仍很难做出短临预报,主要原因为台站分布还是过于稀少,数字化观测后,很多仪器是没有近距离经历过地震,而无典型的震例。建议在今后的震情跟踪过程中多与邻近省局进行异常资料沟通,必要时可以举行联合会商,争取更可靠的研判震情。

Abstract:: Through retrospective summary on the relevant tracing analysis of Menyuan M_S6.4 earthquake on Jan.21,2016,we extracted the background anomaly,such as M≥6 earthquakes calm in 69 months before Yushu M_S7.1 earthquake on Apr.14 since 2010,the low-frequency anomaly of M3.0 earthquakes in Qilian seismic belt,low b value,high GL value,the consistency of focal mechanism,cross fault deformation etc.. However,the confirmed precursory anomaly was that only the gas radon observation value decreased significantly in Ledu Station which is about 140 km from the epicenter since Dec.19,2015. Collecting the post-earthquake data,we extracted the two suspected anomalies,such as the static water level in Pingan Station and the borehole deformation in Huangyuan Station in Qinghai Province. Furthermore,we collected 7 medium-term anomalies in Gansu Province,but their epicenter distance is far away. Comprehensive analyzing all the anomalies,we find that it is difficult to do the short-impending prediction in the today's observation process. Its main reason is that the stations are too few,and many instruments after digital transformation almost not record strong earthquakes,and haven't accumulate typical earthquake examples. Therefore,it is suggest that we should communicate anomaly data with more adjacent provinces in the process of earthquake tracing in the future. If it necessary,we could hold a joint consultation to do more reliably analysis on strong earthquake trend.