吉林松原M≥5.0震群前地磁谐波振幅比异常特征

以东北地区(40°—50°N,120°—130°E)为研究区域,利用黑龙江、吉林和辽宁地区地磁观测数据,进行谐波振幅比计算,对2013年10月31日至11月23日吉林松原接连发生的5个M≥5.0震群前该研究区地下电性结构进行分析,发现:(1)在该区域内显著地震发生前,望奎、通河、三岗、通化和铁岭地震台均出现下降—转折—恢复的异常变化特征,持续时间1—4.5年,变化幅度为0.04—0.07,而通河台Y_(ZH_y)项的不同周期间存在不同步现象,且异常持续2年以上;(2)通河台分钟值谐波振幅比具有由深至浅的周期迁移特征,三岗台秒值数据结果 Y_(ZH_y)向具有由浅入深的迁移特征;(3)2014年3月至2016年4月通河台水平方向的EW向数据不同深度介质电性出现差异性异常,可能预示着该台周边具有发生中强地震的危险,应重点关注该异常变化。

About the anomaly characteristics of amplitude ratio of geomagnetic harmonic wave before Songyuan M≥5.0 earthquake swarm in Jilin Province

In this paper, taking Northeast China (40°-50° N, 120° -130° E) as the research object, with harmonic amplitude ratio method, the geomagnetic data of Heilongjiang, Jilin and Liaoning area, from October 31 to November 23, 2013, before five M≥5 earthquake swarms occurred in Songyuan, Jilin, are analyzed for the investigation of underground electrical structure in the area. It is found that:(1) before a significant earthquake occurred within the region, abnormal changes as "turning down recovery" appeared at Wangkui, Tohe, Sangang, Tonghua and Tieling stations. The durations of changes were 1 to 4.5 years, and the amplitudes were 0.04-0.07. At the same time, there is desynchronic phenomenon of Y_ZHy item of different periods at Tohe station, and the duration there was more than two years. (2) The migration feature of harmonic amplitude ratio of minute value at Tohe is periodic (from deep to shallow), while Y_ZHy result of second value of Sangang station shows migration feature from shallower to deeper. (3)The data of horizontal EW component at Tohe station from March 2014 to April 2016 show different electric anomalies in different depth, implying the risk of strong earthquakes surrounding the station. Much attention should be paid to the anomaly.