Detection of Effects of Shallow Major Earthquakes (M ≥ 5.0, depth ≤ 30 km) Occurred in India, Nepal, and China on Ionosphere Using Statistical Approaches

Using the quartile-based statistical' as this approach is used in the present study approach G-PS-VTEC data of the Lhasa observing station (Geographical Lat. 29.66° N, Geographical Long. 91.10° E) are analysed for six months from July 1, 2019, to December 31, 2019, in the light of eleven major shallow earthquakes (M ≥ 5.0, depth < 30 km) occurred in India, Nepal, and China within a radius of 1500 km assuming it as a center. The results of the analysis show anomalous TEC enhancements of 0.08–15.26 TECU, 1–28 days before the occurrence of these earthquakes. The percentage of TEC enhancements seen before these earthquakes range from 0.74–113.20%. Co-seismic TEC enhancements are also noted for the earthquakes (M = 5, 5.4, 5, 5.3, 5) of August 11, 31, 2019, September 7, 2019, October 27, 2019, and December 9, 2019. The range of co-seismic TEC enhancements is 0.01–4.25 TECU and percentage range of these enhancements is 0.07–31.08%. The post TEC enhancements are observed for the seismic events. The range of post TEC enhancements and percentage enhancements in it are 0.12–6.54 TECU and 1.52–36.41% respectively and the duration of these enhancements is found to vary from 1–21 days. Further, these enhancements in TEC data are also examined in the light of magnetic storms and solar activity and it is found that none of these enhancements are associated with solar activity and magnetic storms. The anomalous days are also confirmed by one more statistical technique. Finally, the possible generation and propagation mechanisms for the observed anomalies are also discussed.