Investigation of ionospheric TEC changes potentially related to Seferihisar-Izmir earthquake (30 October 2020, MW 6.6)

It is important to be able to predict the occurrence time of an earthquake in order to take measures against its destructive effects. One of the parameters to be considered in earthquake prediction is ionospheric changes. Numerous studies have shown some changes in the ionosphere layer before or after the earthquake. These changes can be modelled to be detected with different methods and devices. One of the main parameters in examining these methods is the change of the Total Electron Content (TEC). With Global Navigation Satellite Systems (GNSS) observations, the TEC changes in the ionosphere can be determined before, during and after the earthquake. In this study, the changes in the ionosphere caused by the Seferihisar-Izmir earthquake (37.8881° N 26.7770° E, 30 October 2020, MW 6.6) were investigated in a 58-day time interval, including pre-earthquake, earthquake day, and post-earthquake. Firstly, the indices of solar activity (F10.7), Geomagnetic Activity (Dst), and Geomagnetic Storm (Kp) that can affect the ionosphere change pre-earthquake, earthquake day, and post-earthquake were examined. Then, the effects of the earthquake on the TEC changes in the ionosphere were investigated with the TEC values obtained from the regional ionospheric TEC (RIM-TEC), obtained from GNSS receivers in the earthquake zone and its surroundings, and global TEC maps (CODE). The indices showed that there were no geomagnetic activities between 29 September and 25 November 2020. In the study carried out, it was concluded that it is more accurate to calculate TEC values regionally rather than from Global TEC maps in the case of major episodic effects such as earthquakes. In addition, in the results about the TEC anomaly,it would seem that there was a maximum anomaly 8 days before the 304th day of 2020.