地震地磁观测与研究2025，Vol.46Issue(1)：1-12,12.DOI:10.3969/j.issn.1003-3246.2025.01.001
丽江极低频观测背景变化及基于视电阻率的地震异常回溯分析
Background variation of Lijiang ELF observation and the retrospective analysis of earthquake anomaly based on apparent resistivity
摘要
Abstract
To obtain more comprehensive anomaly information on earthquakes,China has built a multi-parameter,wide-band signal extremely low frequency(ELF)electromagnetic observation network.However,due to the complex format and huge amount of ELF observation data,the valuable data monitored over the years has not been used effectively in earthquake monitoring and prediction.Taking the Yunnan Lijiang ELF Station as an example,this study introduces the observation data and the background change characteristics and uses the apparent resistivity morphology method to retrospectively analyze M≥5 earthquakes around the station.The following findings were made:①From the change of the electromagnetic field power spectrum with frequency at Lijiang Seismic Station,it is found that the five components have similar change forms.The horizontal electric field changes at the same order of magnitude,and the horizontal magnetic field changes at the same order of magnitude,but the vertical magnetic field intensity is lower.② From the temporal variation of the electromagnetic field power spectrum at Lijiang Seismic Station,it can be seen that the five components synchronously show an annual periodicity of high in summer and low in winter.③From the changes of resistivity and phase with frequency at Lijiang Seismic Station,it can be seen that Lijiang has complex electrical structure characteristics.The resistivity value at low frequency(deep)is low,and 0.1-100 Hz is a relatively stable frequency band.④From the temporal variation of the apparent resistivity of Lijiang Seismic Station,we can see that the apparent resistivity presents an annual variation pattern of"low in summer and high in winter",and the annual variation becomes more obvious as the frequency increases.⑤ Before or during strong earthquakes,the apparent resistivity of Lijiang Seismic Station mostly shows abnormal phenomena such as pulsed increase,accelerated decline/rise,and annual distortion,and the abnormal phenomena in the medium and high-frequency bands are the most obvious.The construction of the ELF stations has realized the dynamic observation of electrical structures and electromagnetic fields and improved the ability to identify and capture electromagnetic anomalies related to seismic activities.Based on the analysis of the basic data of Lijiang Seismic Station and the review of historical earthquake cases,this paper summarizes the variation characteristics of apparent resistivity in different frequency bands in different earthquake events,which is conducive to the effective identification of electromagnetic anomalies related to earthquakes and lays the foundation for the application of the ELF data in earthquake tracking and consultation.关键词
极低频电磁/丽江地震台/背景变化/震例回溯/异常识别Key words
the ELF electromagnetic/Lijiang Seismic Station/background variation/earthquake review/anomaly identification引用本文复制引用
范晔,韩盈,韩冰,王立凤,汤吉..丽江极低频观测背景变化及基于视电阻率的地震异常回溯分析[J].地震地磁观测与研究,2025,46(1):1-12,12.基金项目
2024年震情跟踪定向工作任务(项目编号:2024010401) （项目编号:2024010401）
