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
Abstract
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.