在2021年12月22日常州ML 4.6地震前，江苏省南京、江宁、高邮地震台以及海安地震台的顾庄和桑周观测点NS向地电阻率傅里叶滑动去年变曲线均存在显著震前异常。为验证异常可靠性，统计江苏及周边地区地电阻率异常震例，拟合江苏地电阻率最大可探测距离Δmax和震级M的经验公式：lgΔmax=1.0861+0.2624M，获得可引起地电阻率异常变化的显著地震的界定公式：M>（lgΔ-1.0861）/0.2624；对5个站点周边的显著地震和常州ML 4.6地震前存在异常的NS向地电阻率去年变曲线变化进行相关性分析，结果表明，地电阻率异常变化和显著地震有较好的相关性：在地震活动平静期，地电阻率曲线相对稳定，而在显著地震活动前则出现相对明显的异常变化，且下降变化居多，在较强地震活动前下降异常尤为显著，如2016年10月20日射阳ML 4.8地震、2021年11月17日南黄海ML 5.5和12月22日常州ML 4.6地震。因此，南京、江宁、高邮地震台和顾庄、桑周观测点在常州ML 4.6地震前地电阻率异常变化真实可信。
Nanjing Seismic Station, Jiangning Seismic Station, Gaoyou Seismic Station, Guzhuang Seismic Station, and Sangzhou Seismic Station in Jiangsu Province showed relatively consistent stress changes before the Changzhou ML 4.6 earthquake on December 22, 2021. The sliding Fourier spectrum of the NS-direction earth resistivity at each seismic station showed significant pre-earthquake anomalies. In order to verify the reliability of the anomalies, the following work was carried out:firstly, the empirical formula suitable for Jiangsu Province for the maximum epicenter distance Δmax of detectable earth resistivity anomalies and earthquake intensity M is obtained by the method of collecting historical earthquake cases related to the changes of earth resistivity anomalies in Jiangsu Province and its adjacent areas:lgΔmax=1.0861 + 0.2624 M. When the epicenter distance is Δ, the earthquake with M > (lgΔ-1.0861)/0.2624 is defined as a significant earthquake, which can cause abnormal variations in earth resistivity. Then the correlation analysis between abnormal variations of ground resistivity after eliminating the annual trend and the significant earthquakes around the seismic station is carried out. The analysis results show that there is a good correlation between the earth's resistivity variations and significant earthquakes. It is relatively stable in quiet periods of seismic activity and fluctuates or shows declining changes greatly before significant earthquakes. The abnormal variations are more obvious before stronger seismic activities, such as the Sheyang ML 4.8 earthquake on October 20, 2016, the South Yellow Sea ML 5.5 earthquake on November 17, 2021, and the Changzhou ML 4.6 earthquake on December 22, 2021. Therefore, the anomalous changes in ground resistivity before the Changzhou ML 4.6 earthquake at the Nanjing, Jiangning, and Gaoyou seismic stations, as well as the Guzhuang and Sangzhou seismic stations, are true and reliable.
2023,44（5）: 95-106 收稿日期：2023-04-11
DOI：10.3969/j.issn.1003-3246.2023.05.012
基金项目：地震科技星火计划（项目编号：XH211003）
作者简介：张贵霞(1970-),女,副研究员,主要从事地震电磁学研究工作。E-mail:9500828@qq.com
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