Monitoring the TEC Variation Using GPS Dual Frequency System During Quiet and Disturbed Day

The Global Positioning System (GPS) has become a powerful tool for ionospheric studies. The parameter of the ionosphere that produces most of the effects on radio signals is the total electron content (TEC). This paper reports on the variability of the total electron content (TEC) during the North Sumatra earthquake of 26 December 2004 with a magnitude of 9.3 Richter scale. TEC is measured 7 days before and 6 days after the earthquake. The GPS data is taken from JUPEM (Malaysian mapping and Geodesy department). Four sets of data are selected from different GPS satellites that passed near the earthquake location. Results show that earthquake precursors can be seen at nighttime and early morning beginning from 21 December 2004, which is five days before the occurrence of earthquake until one day before the earthquake, which is on 25 December 2004. The results show a good agreement with other researchers who studied other earthquakes.