Ionospheric pre-cursors observed over low latitudes during some of the recent major earthquakes

Earthquakes still occupy first place in the list of natural disasters causing fatal incidences and in loss of human lives and to minimize these losses researchers are trying to find a reliable precursor. The present study reports the ionospheric perturbations, if any, observed over a low-latitude station, Delhi (28.6N; 77.2E), prior to occurrences of 11 major earthquakes (magnitude greater than 6 on Rector Scale) during last couple of years. Initially, foF2 data are analyzed with upper and lower bound of inter-quartile range (IQR) and the observed anomalous changes related to geomagnetic disturbances are filtered out. Then the remaining perturbations are analyzed in relation to the occurrence of seismic activities. The results of the study show some unusual perturbations observed in foF2 values, 1–25 days before and 2–3 days after the main shock of every earthquake indicating a clear seismo-ionospheric link and may be used as earthquake precursors. The present results are in line with previous observations reported by various researchers.