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Title:: Analysis on Geomagnetic Precursory Characteristics before Qinghai Menyuan M_S6.4 Earthquake in 2016

Author(s):: LI Xia; LIU Lei; FENG Lili; Earthquake Administration of Qinghai Province,Xining 810001,Qinghai,China

Keywords:: Menyuan M_S6.4 earthquake; tilt; borehole strain; deformation anomalies

摘要:: 以青海、甘肃和四川交界处(30～41°N,90～107°E)为研究区域,对研究区2013～2015年数字地磁资料进行加卸载响应比和逐日比计算,分析2016年青海门源6.4级地震震前异常变化。研究结果表明:门源地震震前29天沿断裂带及其附近台站地磁加卸载响应比和逐日比均成组出现超限的高值,且异常高值的空间分布都相对集中于震中区附近,震中位于异常高、低值转换带或过渡带附近,表现出一定的时空同步性。与2013年7月22日岷县—漳县6.6级地震前加卸载响应比和逐日比特征变化进行对比分析,发现两者具有一定相似性。因此,地磁垂直分量日变形态及相关计算方法在短期内具有一定预报效能。

Abstract:: Taking the juncture areas(30～41°N,90～107°E)of Qinghai,Gansu and Sichuan as the study area,we analyzed the anomalous changes before Menyuan earthquake from 2013 to 2015 by using the methods of geomagnetic vertical component load-unloading response ratio and daily variation amplitude ratio. The results showed that both load-unloading response ratio and daily variation amplitude radio of stations appeared high value along the fault zone and its adjacent area in 29 days before the Menyuan M_S6.4 earthquake,and the spatial distribution of abnormal high values are relatively concentrated in the epicenter area. The epicenter is located in the transition zone of abnormal high and low values or the transition zone,showing a certain time and space synchronization. Compared with Minxian-Zhangxian M_S6.6 earthquake,we found that the variation characteristics of load-unloading response ratio and daily variation amplitude ratio before two earthquakes are similar. So the daily variation of geomagnetic vertical component and the related calculation method have certain prediction efficiency in the short term.