Shukai Wang

To explore the spatiotemporal evolution characteristics of pre-earthquake GPS TEC anomalies and their correlation with seismic activities, a statistical analysis was performed on pre-earthquake ionospheric GPS TEC anomalies associated with Ms ≥ 6.0 earthquakes in Mainland China from 2012 to 2022 using GPS TEC observational data. Two statistical metrics were adopted, namely average anomaly frequency and anomaly earthquake percentage. Classified statistical analyses were carried out from the perspectives of anomaly polarity, earthquake magnitude, focal depth, and different azimuths of the epicenter to systematically investigate the evolutionary characteristics of TEC anomalies from 30 days pre-earthquake to the earthquake day. The results show that the two core statistical indicators of pre-earthquake TEC anomalies present a significant increasing trend around the 25th, 15th, and 5th days before the earthquake and on the earthquake day. Moreover, the values of the two metrics corresponding to positive pre-earthquake TEC anomalies were higher than those corresponding to negative anomalies. Specifically, the values of the two metrics for pre-earthquake TEC anomalies of strong earthquakes with 6.8–7.6 were higher than those for 6.0–6.8 earthquakes. The spatial distribution of pre-earthquake TEC anomalies is characterized by inhomogeneity and time-dependent characteristics. Compared with earthquakes at a focal depth of 0–10 km, earthquakes at a focal depth of 10–20 km show more significant pre-earthquake TEC anomaly signals. Perturbation characteristics of pre-earthquake ionospheric GPS TEC were statistically analyzed, providing a reference for further elucidating the seismo-ionospheric coupling mechanism and identifying ionospheric precursors of earthquakes.

Anomalous ionospheric disturbances have been observed as potential precursors to earthquakes. This study utilized data from the CSES satellite to investigate anomalies in the ULF band ionospheric electric field and electron density preceding earthquakes with magnitudes of Ms ≥ 6.0 in China and neighboring regions from 2019 to 2021. Comparative analysis with a randomly generated earthquake catalog indicated that these anomalies were spatially concentrated over the epicenter and temporally clustered on specific dates prior to the events. To assess the global relevance of these findings, the analysis was extended to earthquakes with Ms ≥ 7.0 worldwide during the same period, revealing consistent spatiotemporal patterns of ionospheric anomalies in both regional and global datasets. Furthermore, by combining the two earthquake catalogs and classifying events into oceanic and continental categories, additional statistical analyses were conducted to identify distinct ionospheric disturbance patterns associated with these different tectonic environments. These results provide a solid foundation for future research aimed at identifying and extracting ionospheric anomalies as potential pre-earthquake indicators.