Abstract:
Spatial and temporal characteristics of Rayleigh wave generated ionospheric perturbations are well documented based on the ionospheric measurements using Global Positioning System (GPS)-Total Electron Content (TEC) technique. However, due to integrated nature of the GPS recorded TEC, the actual detection altitudes of these perturbations could not be determined. In general, the maximum electron density altitude (hmF2) is assumed as the perturbation detection altitude in GPS-TEC. To validate this assumption, case studies focusing on the early detection of ionospheric perturbations induced by direct epicentral waves during the Mw 7.4 9 March 2011 Sanriku-Oki and Mw 9.0 11 March 2011 Tohoku-Oki earthquakes were performed. In the present study, we attempt to estimate the detection altitudes of GPS-TEC derived ionospheric perturbations generated by the propagating Rayleigh surface waves following the Mw 9.0 11 March 2011 Tohoku-Oki earthquake. Based on the 3D ray tracing of Rayleigh wave generated acoustic waves in the atmosphere and realistic GPS station-satellite line of sight geometry, we could efficaciously compute the actual detection altitudes of Rayleigh wave generated coseismic ionospheric perturbations (CIPs). Further, our study also demonstrates the possible detection of CIPs progressively at different altitudes based on varying satellite geometries.
