Abstract 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 diff erences 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 diff erential response reveals the modulating eff ect 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 amplifi cation 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.
Fund: This research was 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), and the National Natural Science Foundation of China (No. 41274079).
About author: Zhang Lei is a Senior Engineer at the Hebei Earthquake Agency. He holds a Master's degree in Geological Engineering. His research focuses on seismology and seismic geology, with particular interests in extraction of earthquake anomaly, earthquake mechanism analysis, and the study of active tectonic structures.
Cite this article:
. Characteristics of geomagnetic anomalous evolution before and after two major earthquakes: a Taylor polynomial model analysis[J]. APPLIED GEOPHYSICS, 2025, 22(4): 1233-1242.
2025, Vol. 22 
