The catastrophic seismic events of the last decades push forward the necessity to explore new techniques for source estimation, oceanic tsunami tracking, as well as tsunami warning systems. Early observations of the Rayleigh wave signature in the ionosphere by Doppler sounder were able to measure lithospheric properties, sounding the atmosphere at 200 km of altitude. After the Sumatra event (26 December 2004) , the successful tsunami detection by altimeters validates the possibility of tsunami

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... etection by ionospheric sounding. Today, the catastrophic tsunamigenic earthquake in Tohoku (11 March 2011) strongly affirms the potential of ionospheric sounding to visualize the vertical displacement of the ground and ocean: the Japanese GPS network, GEONET, imaged the source extent 8 min after the rupture; it also visualizes the radiation pattern and Rayleigh waves over the entire Japan, including the oceanic region overlooking the rupture; in the far field, the airglow camera located in Hawaii showed the internal gravity wave forced by the tsunami propagating in a zone of 180 ×180 km 2 around the island. The ionospheric sounding potential of 2D visualization could extend the present vision of seismology. This work highlights the actual capability and the potential improvement suggested by ionospheric seismology. 9