Earth Planets Space, Vol. 63 (No. 7), pp. 881-884, 2011
C. H. Chen1, A. Saito1, C. H. Lin2, J. Y. Liu3,4,5, H. F. Tsai6, T. Tsugawa7, Y. Otsuka8, M. Nishioka8, and M. Matsumura1
1Department of Geophysics, Kyoto University, Japan
2Department of Earth Science, National Cheng Kung University, Taiwan
3Institute of Space Science, National Central University, Taiwan
4Center for Space and Remote Sensing Research, National Central University, Taiwan
5National Space Organization, Taiwan
6Taiwan Analysis Center for COSMIC (TACC), Central Weather Bureau, Taiwan
7National Institute of Information and Communications Technology, Japan
8Solar-Terrestrial Environment Laboratory, Nagoya University, Japan
(Received April 10, 2011; Revised June 15, 2011; Accepted June 16, 2011; Online published September 27, 2011)
Propagation of the initial ionospheric total electron content (TEC) disturbances generated by the 2011 off the Pacific coast of Tohoku Earthquake at 05:46:23 UT on March 11, 2011, was investigated with ground-based Global Positioning System (GPS) receivers in the east-Asian region. It was found that the initial ionospheric disturbance formed a zonal wave front after the earthquake occurrence. Four zonal wave fronts of this initial ionospheric disturbance were observed to travel southward from Japan to Taiwan with a velocity of about 1,000-1,700 m/s. This study further found that the direction of the wave vector rotated from the south-southwest to the south-southeast as it traveled from Japan to Taiwan. The meridional propagation of the coseismic ionospheric disturbances is consistent with those observed after previous intense earthquakes. The temporal evolutions of initial ionospheric disturbances, after the earthquake, near the epicenter was observed in two-dimensions. The directivity of the disturbances was caused by a geomagnetic field effect.
Key words: Ionospheric TEC disturbance, Tohoku Earthquake.