Anomalies observed in TEC and foF2 data related to large magnitude earthquakes occurred in the year 2007

In this paper, we have studied the effect of earthquakes on Total Electron Content (TEC) data of the year 2007 at Agra (Geographic Lat. 27.2°N, Long. 78°E), India. The measurements of TEC are made by using a dual frequency GPS receiver system. We found 39 cases of earthquakes (M≥5.0) in the range of 2000 km from the observing station at Agra. It is observed that the TEC shows anomalous behavior in the form of enhancement and depletion 0–9 days prior to the occurrence of these earthquakes. We also study the simultaneous variation of foF2 and TEC for the months of May and June, 2007. The foF2 data exhibit enhanced anomaly on the same day of a large magnitude earthquake (M=6.0) in May, 2007 while for the same case of earthquake TEC shows anomaly before 02 days in the form of enhancement. The atmospheric oscillations and electric field generation during the earthquake preparation process may be the significant contributors of these anomalies in TEC and foF2 data.