2-D ionosphere TEC anomaly before January 28, 2020, Cuba earthquake observed from a network of GPS observations data

Global Positioning System (GPS) observations from 118 Continuously Operating Reference Stations (CORS) were used to study total electron content (TEC) variations in the earth’s ionosphere before the occurrence of Mw 7.7 Cuba earthquake on January 28, 2020. The spatial distribution of ionosphere TEC anomaly in 2 dimensions with distance from the observation stations is studied in the present analysis. TEC time series from the nearest observation station suggests abnormalities in TEC variations on January 19–20, 2020. At 19.20 UTC on January 19, 2020, a low TEC value was observed at CORS, close to the earthquake epicenter. The epicenter lies approximately 90 km from the center of the anomaly zone (low TEC). The anomaly zone’s size was about 725 km in radius. The study suggests the possibility of observing TEC anomaly zone in the ionosphere a few days before an earthquake occurs. The study indicated that TEC anomaly zone developed in the ionosphere may have resulted from stress development on the crustal rocks supporting the presence of LAIC mechanism. The analysis also showed that TEC might change due to other unknown sources apart from the seismic origin. Overall, the study suggests TEC monitoring with a dense CORS network may help identify the anomaly zone spatially in 2 dimensions before an earthquake occurs. The anomaly zone may coincide with the earthquake epicenter, and hence, the techniques may be essential for studying the TEC-earthquake epicenter relationship.