Seismo-Ionospheric Precursors of the 26 December 2006 M 7.0 Pingtung Earthquake Doublet

  • Author(s): Jann-Yenq Liu, Sen-Wen Chen, Yao-Chun Chen, Horng-Yuan Yen, Chung-Pai Chang, Wen-Yen Chang, Lung-Chih Tsai, Chia-Hung Chen, and Wen-Hsi Yang
  • DOI:


  • Keywords: Seismo-ionospheric precursor, Ionosphere, Total electron content, NmF2, Doppler sounding system



Anetwork 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 above Taiwan. Two M 7.0 offshore earthquakes occurred near Pingtung, the most southern county of Taiwan, on 26 December 2006. Analysis has revealed that the ionospheric TEC and F2-pear electron density (NmF2) surrounding the epicenters of the events decreased abnormally in the afternoon of the fourth day before the earthquakes, and quasi 3-minute fluctuations of pronounced vertical motion in the ionosphere also appeared over the last two days prior to the earthquakes. This is for the first time the pre-earthquake fluctuation signatures in the ionosphere being reported.

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