[S20-1] Earth and planetary space and remote sensing seismology; i.e., seismology without seismometers

[S20-1-04] Inversion of the GPS -TEC induced by tsunami in order to estimate the sea level anomaly using a the normal mode modeling

^○Virgile Rakoto¹, Philippe Lognonne¹, Lucie Rolland² (1.Institut de physique du globe de Paris, Paris, France, 2.Universite Cote d Azur, OCA, CNRS, IRD, Geoazur, Valbonne, France)

Large underwater earthquakes (Mw > 7) can transmit part of their energy to the surrounding ocean through large sea-floor motions, generating tsunamis that propagate over long distances. The forcing effect of tsunami waves on the atmosphere generate internal gravity waves. When they reach the upper atmosphere THIS produce ionospheric perturbations . Theses perturbations are frequently observed in the total electron content (TEC) measured by the multi-frequency Global navigation Satellite systems (GNSS) data (e.g., GPS,GLONASS and the future GALILEO. In this paper, we performed for the first time an inversion of the sea level variation using the GPS TEC data using a least square inversion (LSQ) through a normal modes summation modeling technique. Using the tsunami of the 2012 Haida Gwaii in far field as a test case, we showed that the amplitude peak to peak of the sea level variation inverted using this method can be compared with less than 10 % error to the one measured by a dart buoy. Nevertheless, we cannot yet at this time invert the second wave arriving 20 minutes later. This second wave is indeed generaly explain by the coastal reflection which SPHERICAL normal modeling does not take into account. Our technique is then applied to two other tsunamis : the 2006 Kuril Islands tsunami in far field, and the 2011 Tohoku tsunami in closer field. This demonstrates that the inversion using a normal mode approach is able to estimate fairly well the amplitude and waveform first arrivals of the tsunami waveform.