Keywords:ionospheric total electron content, tsunami early warning, global navigation satellite system
Tsunami waves can induce Tsunami Traveling Ionospheric Disturbances (TTIDs) of the total electron content (TEC). In this study, we examine the TEC derived by ground-based receivers of the global positioning system (GPS) and identify TTIDs induced by 2004 Indian Ocean tsunami. Simulations of the COMCOT (Cornell Multi-grid Coupled Tsunami) model and analyses of the circle method, the ray-tracing technique, and the beam-forming technique are used to show that TTIDs can be quickly detected and confirmed after the tsunami occurrence. Finally, the ionospheric TEC derived by existing ground-based GNSS (global navigation satellite systems) receiving stations is demonstrated to be useful to support the tsunami early warning system.