Application of Probability and Statistics on GNSS Data to Analyze TEC Anomalies Generated by Earthquakes

Ionospheric disturbances are associated with the propagation of seismic waves generated by earthquakes. We analyze total electron content (TEC) fluctuations from Global Navigation Satellite Systems (GNSS) data. This study investigates the global earthquakes from December 2004 to March 2020 with magnitude (Mw) 4.0 to 9.1. Data of 65 permanent GNSS stations are used to analyze the impacts of these earthquakes on the ionosphere. The experimental data based on the cluster sampling method ensure strict conditions such as accuracy, the distance from the monitoring stations to the epicenter, and the depth of the hypocenter. At least three GNSS stations near the epicenter participate in the analysis of each earthquake. Probability and statistics are applied to remove outliers and rough errors in the input data, to select datasets with similar quality, and to analyze TEC anomalies. The results show that when a strong earthquake occurs, the TEC values calculated at different GNSS stations surrounding the earthquake region tend to exhibit similar variations. Depending on the magnitude, epicenter, and hypocenter depth, these fluctuations can range from ± 3.2 TECU to ± 14.5 TECU for large earthquakes. These TEC fluctuations occur from 30 min to almost two hours before the mainshock of the earthquakes and last to the aftershock period. For earthquakes with a magnitude greater than 6.0 Mw, the TEC fluctuations are significant. The findings of this study contribute to GNSS applications in studying earthquakes in the future.