Ionospheric GPS TEC Anomalies

Ionospheric GPS TEC Anomalies and M ³ 5.9 Earthquakes in
Indonesia during 1993 - 2002

Sarmoko Saroso
1
, Jann-Yenq Liu
2, 3
, Katsumi Hattori
4, *
, and Chia-Hung Chen

National Institute of Aeronautics and Space (LAPAN), Bandung, Indonesia
2
Institute of Space Science, National Central University, Chung-Li, Taiwan, ROC
3
Center for Space and Remote Sensing Research, National Central University, Chung-Li, Taiwan, ROC
4
Department of Earth Sciences, Graduate School of Science, Chiba University, Chiba, Japan

Received 15 August 2007, accepted 22 November 2007

ABSTRACT
Indonesia is one of the most seismically active regions in the world, containing numerous active volcanoes and subject to frequent earthquakes with epicenters distributed along the same regions as volcanoes. In this paper, a case study is carried out to investigate pre-earthquake ionospheric anomalies in total electron content (TEC) during the Sulawesi earthquakes of 1993 - 2002, and the Sumatra-Andaman earthquake of 26 December 2004, the largest earthquake in the world since 1964. It is
found that the ionospheric TECs remarkably decrease within 2 - 7 days before the earthquakes, and for the very powerful Sumatra-Andaman earthquake, the anomalies extend up to about 1600 km from the epicenter.
Key words: GPS TEC (Total Electron Content), Pre-earthquake-related anomaly, The Sulawesi earthquakes, The 2004 Sumatra-Andaman