Tsunami-induced phase and amplitude perturbations of subionospheric VLF signals

A network of VLF receivers, sited in the Far East, has been used to observe the response of the lower ionosphere to tsunamis resulting from the November 15, 2006 (Kuril region) and the March 11, 2011 (Tohoku region) earthquakes. Specific perturbations in the phase and amplitude of VLF signals have been found for both cases. A qualitative interpretation of the observed effects is suggested in terms of the interaction of internal gravity waves with lower ionosphere.