Seismo-traveling ionospheric disturbances of ionograms observed during the 2011 M_w 9.0 Tohoku Earthquake

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.