摘要
This study systematically analyzed the spatiotemporal evolution characteristics of geomagnetic anomalies before and after the 2013 Sichuan Lushan M7.0 earthquake and the Gansu Minxian M6.6 earthquake by constructing a geomagnetic diurnal variation model based on Taylor polynomial fitting,combined with midnight mean values of the geomagnetic F component from China,s geomagnetic observatory network.The results reveal distinct differences in anomaly patterns,namely per-sistent positive anomalies were observed in the epicentral region of the Lushan earthquake,while significant negative anomalies characterized the Minxian earthquake zone.This differential response reveals the modulating effect of the electrical structure of the seismogenic medium on space electromagnetic disturbances,namely positive anomalies may correspond to the stage of stable stress accumulation in intact rock,while the expansion of negative anomalies may reflect an amplification of electromagnetic disturbances induced by fracture expansion.Further analysis demonstrates that both anomalies exhibit a three-stage evolutionary pattern,namely pre-seismic accumulation,co-seismic release,and post-seismic adjustment.The phase transitions in these anomalies are closely correlated with regional tectonic stress accumulation and destabilization processes.These findings not only provide new evidence for the physical interpretation of seismomagnetic precursors but also establish a theoretical foundation for developing earthquake prediction methods based on the dynamic evolution of geomagnetic anomalies.
本研究通过构建泰勒多项式拟合的地磁场日变化模型,利用中国地磁台网总场F分量子夜均值数据,系统分析了2013年四川芦山7.0级地震与甘肃岷县6.6级强震前后地磁异常的时空演化规律。研究发现:芦山地震震中区呈现持续性正异常,岷县地震区则表现为负异常,这种差异揭示了震源介质电性结构对空间电磁扰动的调制作用,即正异常可能对应完整岩体中应力稳定积累的阶段,而负异常扩大可能反映裂隙扩张所诱发电磁扰动的增强;进一步分析表明,两类异常基本呈现“震前累积-同震释放-震后调整”的三阶段演化特征,其阶段性转折与区域构造应力积累-失稳过程较吻合。研究结果不仅为地震地磁前兆物理解释提供了初步的新证据,也为构建基于地磁异常演化的地震预测方法奠定了理论基础。
基金
supported by a Collaborative Project of the National Natural Science Foundation of China on Technical Maintenance and Data Preprocessing of the GPS Observation Array for the Qiaojia Earthquake(No.0120603)
the National Natural Science Foundation of China(No.41274079).
