Earth Planets Space, Vol. 63 (No. 7), pp. 859-862, 2011
Ho-Fang Tsai1,2, Jann-Yenq Liu3,4,5, Chien-Hung Lin6, and Chia-Hung Chen7
1Taiwan Analysis Center for COSMIC (TACC), Central Weather Bureau, Taipei, Taiwan
2GPS Scientific Application Research Center (GPS-ARC), National Central University, Jhongli City, Taiwan
3Institute of Space Science, National Central University, Jhongli City, Taiwan
4Center for Space and Remote Sensing Research, National Central University, Jhongli City, Taiwan
5National Space Organization, Hsinchu, Taiwan
6Department of Earth Science, National Cheng Kung University, Tainan, Taiwan
7Department of Geophysics, Kyoto University, Kyoto, Japan
(Received April 8, 2011; Revised June 14, 2011; Accepted June 15, 2011; Online published September 27, 2011)
The global positioning system (GPS) can be used to monitor the seismic perturbation induced by the 2011 off the Pacific coast of Tohoku Earthquake (magnitude 9.0), Japan, on March 11, 2011, and to trace the tsunami across the Pacific Ocean by measuring the changes in the ionospheric total electron content (TEC). We estimate the vertical and horizontal mean speeds of the seismic and tsunami waves using the time and distance of the TEC perturbation, and then, taking into account those determined speeds, trace back to the epicenter and the tsunami origin by applying a 3-dimensional spherical model. The results show that both the tracked epicenter and the tsunami origin are quite close to the epicenter reported by the USGS, with a mean horizontal propagation speed of 2.3 km/s after the earthquake and about 210 m/s after the tsunami. This consistency confirms that the perturbation sources in the ionosphere are due to the earthquake. This implies that the GPS-TEC measurements have the potential to be part of a lower cost, ground-based, tsunami monitoring system.
Key words: GPS, ionospheric total electron content, TEC, tsunami, 2011 Tohoku earthquake.