Ionospheric Total Electron Content Response to the December 26, 2004 North Sumatra Earthquake

Problem statement: Ionospheric precursors of earthquake have been studied by scientists and seismologists. This study aims at examining the relationship between the ionosphere and earthquake precursors. The effects of the anomalous electric field that penetrates the ionosphere on the electron concentration can be measured experimentally. This study reports on the variability of the Total Electron Content (TEC) during the December 26, 2004 earthquake in North Sumatra (epicentre: 3.295°N, 95.982°E) which measured 9.3 on the Richter scale. Approach: The ionospheric TEC near North Sumatra between December 19 to 31 was calculated between 22:00 and 24:00 and between 02:00 and 06:00 local time (LT) using a dual frequency Global Positioning System (GPS) receiver. It was recorded for a period of 13 days, which is seven days before and five days after the earthquake. The GPS data was taken from the Department of Survey and Mapping Malaysia in the north of Malaysia (4.1°N, 99.8°E), which is near North Sumatra. Four sets of data were selected from different GPS satellites that passed near the epicentre. Results: Results show good agreement with the existence of earthquake precursors. TEC variability was detected at night and in the early morning of 21 December 2004 (five days before the earthquake) and 25 December 2004 (a day before). Findings show an increase in the electron concentration level at the station closest to the epicentre and the TEC varies from 2-10 TEC unit. Conclusion/Recommendations:   The findings correspond with previous research and literature in this field. Further studies on the parameters that cause the change in the ionospheric TEC due to earthquakes are needed if this is to be used as part of an earthquake early warning prediction system.