Seismo-Ionospheric Precursors of the December 26, 2006 M7.0 Pingtung Earthquake Doublet


Jann-Yenq Liu1,2,*, Sen-Wen Chen1, Yao-Chun Chen1, Horng-Yuan Yen3, Chung-Pai Chang2,3, Wen-Yen Chang4, Lung-Chih Tsai2,1, Chia-Hung Chen1, Wen-Hsi Yang1

1 Institute of Space Science, National Central University, Chung-Li, Taiwan

2 Center for Space and Remote Sensing Research, National Central University, Chung-Li, Taiwan

3 Department of Earth Science and Institute of Geophysics, National Central University, Chung-Li, Taiwan

4 Department of Natural Science, National Science Council, Taipei, Taiwan



    A network of ground-based GPS receivers, an ionosonde, and a Doppler sounding system have been employed to monitor the total electron content (TEC), electron density, and vertical motion of the ionosphere in Taiwan. Two M7.0 offshore earthquakes occurred near Pingtung, the most south county of Taiwan, on December 26, 2006. It is found that the ionospheric TEC and F2-pear electron density (NmF2) around the epicenters abnormally decrease in the afternoon period of day 4 before the earthquakes, and quasi 3-minute fluctuations of the vertical motion also pronouncedly appear 0-2 days prior to the earthquakes. This is for the first time the pre-earthquake fluctuation signatures in the ionosphere being reported.