Analysis of ionospheric response to Earthquake using GPS data: a case study of Chignik, North America and Southern-Sandwich, South America Earthquakes

In this study, GPS-derived total electron content (TEC) data were utilized to monitor ionospheric behaviour 20 days before and 5days after two significant earthquakes that occurred in Chignik, North America and Southern-Sandwich, South America on 10th November 2021 and 8th December 2021 respectively. Data were collected from GPS stations within the seismogenic zone. The sunspot number (SSN) and F10.7 indices were used to track solar activity during the events, while the planetary geomagnetic activity index (kp) and disturbance storm-time (Dst) indices were used to check geomagnetic activity. Results from the analysis revealed that TEC data contain both negative and positive ionospheric anomalies during the investigative period using a statistical analysis technique that involved moving median. Geomagnetic and solar indices indicated relative stillness during 88% of the anomalous days isolated for the earthquakes, hence anomalies were considered seismogenic. The result further suggests that a significantamount of disturbances is caused by seismogenic processes. As earthquake-induced anomalies were found within 20 days of the studied cases, it was also shown by the discovery of earthquake-induced TEC anomalies through temporal analysis that ionospheric fluctuations are crucial for earthquake forecasting. Therefore, this study suggests that there could be a connection between TEC anomalies in the ionospheric space and the occurrence of significant earthquakes. Thus, it is advised that TEC monitoring be seriously taken into account for short-term earthquake event forecasting, particularly in regions with unreliable seismic measurements.