2018年精河5.4级地震前地磁日变化畸变异常分析

2018年10月16日新疆精河5.4级地震发生时,震中附近的台站不同程度上记录了地磁日变化畸变异常,如地磁总强度F02时每日一值空间相关异常、地磁垂直分量加卸载响应比异常、地磁低点位移以及地磁日变化空间相关异常等。统计震前观测到的所有地磁异常,并分析研究了其震前异常变化特征。得到如下结论:(1)从全国每日一值相关分析结果看,震前114天出现每日一值空间相关异常,异常高值台为乌鲁木齐和克拉玛依;(2)震前59天沿北天山断裂带分布的地磁台站加卸载响应比均成组出现超限的高值,且异常高值的空间分布跟震中位置有一定关联;(3)中国大陆地磁台站震前37天出现低点位移突变分界线,且异常集中于震中附近;(4)震前出现地磁垂直分量日变化空间相关异常,异常台站空间上也主要集中于北天山地区。因此地磁垂直分量日变形态及有关的计算方法短期内具有一定的预报效能,可为今后利用地磁方法预测地震积累经验和震例。

Distortion Anomalies in Geomagnetic Diurnal Variationbefore the Jinghe M5.4 Earthquake in 2018

The comprehensive characteristics of geomagnetic anomalies before the Jinghe M5.4 earthquake on October 16, 2018 were obtained and analyzed using a series of geomagnetic methods such as the geomagnetic daily value spatial correlation, geomagnetic load-unload response ratio, spatial correlation of daily variation of the geomagnetic vertical component, and geomagnetic low-point displacement. These methods showed that there were middle and short-term anomalies before the earthquake. Additionally, the results showed the following aspects. (1) Before the earthquake, multiple anomalies existed, which enhanced the credibility of the methods. (2) The anomalies considerably increased closer to when the earthquake erupted demonstrating that seismogenic probability increased in this area. (3) Compared with a single method, a comprehensive analysis method to identify earthquake locations, can reduce the time scale of prediction. (4) Anomalies in the spatial correlation of the daily variation of the geomagnetic vertical component mainly appeared in the northern Tianshan area before the earthquake. The comprehensive anomalies observed in the Jinghe earthquake illustrated that geomagnetic analysis methods had a certain forecast effectiveness in short-term earthquake prediction.