LAUSR

Abstract Statistical analyses on the intensification of seismic precursors before and after the earthquakes (EQs) from Global Navigation Satellite System (GNSS) based Total Electron Content (TEC) may provide evidences about the potential mechanisms of lithosphere-ionosphere coupling. In this paper, ionospheric anomalies before and after 1182 (Mw > 5.0) EQs during 1998–2019 at three different latitudinal zones (80°N–25°N, 25°N–25°S, and 25°S–80°S) are investigated from global GNSS TEC observations. Previous studies proposed different time intervals for the occurrence of TEC anomalies triggered by EQs. In this study, we reveal that prominent TEC anomalies in the form of enhancement and depletion occur within 5 days before and after the main shock of the EQs. Further analysis suggests that the probability of TEC anomalies occurred before EQs of Mw ≥ 6.0 and focal depth of less than 220 km (Zone B) is about 0.8. Similarly, a probability of 0.65 for TEC anomalies is recorded before EQs of Mw ≥ 7.0 and focal depth less than 120 km in Zones-A and C. In our analysis, TEC anomalies generated by EQs are isolated from those produced by the geomagnetic storms through the Kp geomagnetic activity index and the disturbance storm time (Dst) index.