地磁日变化感应电流异常与地震的成组特征初步分析

Preliminary Analysis of Grouping Characteristics between Induced Current Anomalies by Geomagnetic Diurnal and Earthquakes

摘要:

2019年8月10日—2021年4月28日我国南北地震带及附近地区出现了一组57次地磁日变化感应电流线状集中分布与短期原地重现异常,本文研究了其与之后发生的一组6次6级以上地震之间的关系,发现:①整组重叠异常在时间上可大致分为4个阶段,4个阶段的异常空间分布区域具有前后相邻、阶段相连的特征,以及整组异常首尾相连特征,且随时间的迁移有左旋迹象;②整组重叠异常的异常频次和异常面积随时间变化具有同步性,在第1～3阶段,异常累加频次和异常面积逐渐增大至最大值,然后在第4阶段衰减,组内6次地震中的5次,尤其是最大的玛多7.4级地震发生在异常累加频次和异常面积出现最大值之后的衰减期及之后;③地震可能发生在整组异常期间的任何时间,既可能发生在组内单次异常之后2年左右,也可能发生在组内单次异常之后的短期与临震阶段;④整组重叠异常空间分布具有带状特征,地震基本发生在重叠段分布带边缘,以及重叠段端部密集地区或附近。依据重叠异常发生机理,认为成组重叠异常分布带边缘地区是震前1～2年左右出现过“活动”的高导区与介质电性稳定的高阻区之间的电性结构梯度带,不同于相对稳定的电性结构梯度带,其具有重要的地震中期(1～2年左右)甚至短临前兆意义。

Abstract:

From August 10,2019 to April 28,2021,a group of 57 linear concentrated distribution of geomagnetic diurnal induced currents and short-term in-situ recurrence anomalies occurred in North-south seismic zone and its adjacent areas of China. During the same period,a group of 6 earthquakes with magnitude 6.0 or above occurred in this area. The results from the studies of the relationship between them in this paper show that:①The whole group of overlapping anomalies can be roughly divided into four stages with times. The spatial distribution regions of the four stages have the characteristics of successive adjacent stages and the whole group has the characteristics of end to end. The distribution regions of the four stages are of left-rotation character over time. ②The variation of anomalous frequency and anomalous area of the whole group of overlapping anomalies is synchronous with time. The accumulation frequency and anomalous area of the whole group of overlapping anomalies gradually increase to the maximum in the first to third stage,and then decrease in the fourth stage. Five of the six earthquakes in the group,especially the largest one,Maduo 7.4,occurred in the attenuation period after the maximum accumulation frequency and abnormal area. ③Earthquakes may occur at any time during the whole group of anomalies,from about 2 years after a single anomaly in the group,to in the short term and impending stage after a single anomaly in the group;④ The spatial distribution of the whole group of overlapping anomalies is zonal,and the earthquakes basically occur at the edge of the distribution zone of the overlapping segment,at or near the densely populated area at the end of the overlapping segment. Based on overlapping anomaly mechanism we think that group overlap abnormal distribution of edge region is about 1~2 years before region with the guide of "activity" medium electrical stability of the high resistance zone between the electrical structure of the gradient zone,which has an important earthquake medium-term(1~2 years)even short precursory significance,because it is different from the relatively stable electrical gradient structure belt.