2017年吉林宁江M 4.9地震前电磁变化

2017年7月23日吉林宁江M 4.9地震前，地震影响范围内电磁台站出现多种电磁异常，其中4项电磁手段异常明显，分别是：地磁垂直分量日变幅加卸载响应比异常、地磁场总场强度F₂₁每日一值空间相关异常、绥化地震台地电阻率EW向反向下降异常及林甸电阻率EW向整点值变化异常簇异常。本文对地磁异常进行统计、分析，为东北地区未来利用电磁方法分析预测地震提供经验。

The variations of geomagnetic before Jilin Ningjiang M 4.9 earthquake in 2017

Before Jilin Ningjiang M 4.9 earthquake on July 13, 2017, there appeared many kinds of electromagnetic anomalies around the stations in the range of electromagnetic affected by the earthquake. There are four kinds of electromagnet anomalies:geomagnetic daily variation of vertical Z component LURR with high value, the daily value of the F₂₁ component of the total field associated with a low value anomaly, the abnormal resistivity of the reverse change of EW direction and an anomaly cluster of the whole point at EW observation direction at Suihua and Lindian seismic stations in Heilongjiang Province, respectively. In this article, all electromagnetic anomalies before and after the earthquake occurrence are statistically analyzed. Finally we summed up the usage of geomagnetic analysis method for accumulating earthquake prediction experience.