Ionospheric response to Kuril undersea earthquakes according to GPS satellite data

The effects that the two Kuril undersea earthquakes of November 15, 2006, and January 13, 2007, had on the ionosphere are considered on the basis of the results of measurements of variations in the ionosphere’s total electron content obtained from the network of Russian GPS stations. Owing to a favorable location of the stations, the ionosphere’s response to these earthquakes is studied in the vicinity of and far (up to distances on the order of 1000 km) from their epicenters. It is found that the apparent velocity of propagation of ionospheric disturbances (1–3 km/s) significantly exceeds the velocity of propagation of tsunami waves caused by earthquakes; this fact can be used in forecasting tsunamis. It is shown that, in parallel with the known type of ionospheric response to earthquakes in the form of an N-wave, there is also its response in the form of an inverted N-wave in the vicinity of and far from their epicenters. The causes of occurrence of the response in the form of an inverted N-wave are interpreted.