Long-distance traveling ionospheric disturbances caused by the great Sumatra-Andaman earthquake on 26 December 2004

By using data from the GPS network, we observed exceptional intensive quasi-periodical perturbations of the total electron content (TEC) caused by the great Sumatra-Andaman earthquake on 26 December 2004. The time period of the variations was about 15 min, their duration was about 1 hour. The amplitude of the TEC oscillations exceeded the amplitude of “background” fluctuations in this range of periods by one order of magnitude, at a minimum. They were registered 2–7 hours after the main shock at a distance from 1000 to 5000 km, both on the northwest and northeast outward from the epicenter. The most probable source of the observed oscillations appeared to be a seismic airwave generated by the sudden vertical displacement of the Earth’s surface near the epicenter.