Detection and Analyses of Traveling Ionospheric Disturbances from two Successive Earthquakes and Tsunami Waves

Traveling ionospheric disturbances (TIDs), induced by acoustic-gravity waves (AGWs) in the neutral atmosphere, are observable in trans-ionospheric Global Navigation Satellite System (GNSS) measurements. Previous studies on the GNSS-derived ionospheric disturbances have been presented for studying the interactions between ionospheric perturbations associated with the 2011 Japan Tohoku Earthquakes and Tsunamis. Three different types of TIDs were observed. Short-period disturbances (2 - 8 minutes) with speeds up to 2300 km/s were observed in the near-field, and the long-period (8-22 minutes) disturbances with speeds (195 - 354m/s) were identified in both near- and far-fields. In this study, identification and classification of ionospheric disturbances was conducted using a wavelet detection method in combination with a cross-correlation technique estimating the propagation speeds and directions of atmosphere wave-induced disturbances in dual frequency IEC time series collected form GNSS networks near the epicenter of the March 11, 2011 Japan Tohoku earthquake and the subsequent tsunami induced by it. Through the use of the wavelet detection process, we are able to find major wave trains, present in the data collected from these networks, with two dominate frequency bands corresponding to the disturbances from two successive earthquakes and tsunami propagations. Additionally, the comparative observations and model predictions, including ground motions and tsunami propagations calculated by JPL using the MOST model are used to understand and perceive the dominant properties (propagation speeds, directions, periods and occurrence times) of the GPS-derived ionospheric disturbances. This analysis is demonstrated on data from 1235 stations in the Japanese GEONET GPS network. A comparison between GNSS-derived disturbances, ground motions and tsunami propagations shows that the propagation directions and speeds of short-period disturbances are consistent with the acoustic waves triggered by the main-shock and aftershock with different epicenters. The propagation directions and speeds of the long-period disturbances are in agreement with the tsunami propagations.