Earth Planets Space, Vol. 63 (No. 7), pp. 897-902, 2011
Jann-Yenq Liu1,2,3 and Yang-Yi Sun1
1Institute of Space Science, National Central University, No. 300, Jhongda Rd., Jhongli City, Taoyuan County 32001, Taiwan
2Center for Space and Remote Sensing Research, No. 300, Jhongda Rd., Jhongli City, Taoyuan County 32001, Taiwan
3National Space Program Origination, 8 F, No. 9, Prosperity 1st Rd., Hsinchu Science Park, HsinChu, Taiwan
(Received April 7, 2011; Revised May 15, 2011; Accepted May 18, 2011; Online published September 27, 2011)
In this paper, sequences of ionograms recorded by 4 ionosondes in Japan and 1 in Taiwan are employed to examine seismo traveling ionospheric disturbances (STIDs) triggered by the 11 March, 2011, M 9.0 Tohoku Earthquake. The circle method, a standard/traditional technique of seismologists for locating an earthquake, is used to find the origin and compute the propagation speed of the triggered STID. Results show that the STID speeds induced by Rayleigh waves, acoustic gravity waves mainly traveling in the ionosphere, and tsunami waves of the Tohoku Earthquake are 2100-3200 m/s (2.1-3.2 km/s), 900 m/s, and 200 m/s (720 km/hr), respectively. The origins derived by the circle method near the epicenter confirm that the observed STIDs were triggered by the seismic waves and tsunami waves of the Tohoku Earthquake.
Key words: Tohoku Earthquake, seismo-traveling ionospheric disturbances, ionosonde.