Localization of the source of ionospheric disturbance generated during an earthquake

Abstract

[1]  For the first time a method is developed of localization of the source and determination of the characteristics of wave disturbances generated during earthquakes. In the method the disturbances in the total electron content registered at the GPS receiver network are considered as a set of signals of a nonequidistant phased grating of "ionospheric detectors" with known coordinates. As a result of solution of the equation system for the plane and spherical front relative to the measured parameters of the disturbance, the phase velocity of the wave disturbance and also the position and time of switching on of the source are determined. It is found that the ionospheric disturbances generated during strong earthquakes have the form of a spherical wave diverging with a velocity of ~1000 m s^-1 from the "secondary" source localized over the epicenter at the level of the maximum of the ionospheric F2 layer (300-400 km), the time of the source "switching off" delaying relatively the main seismic shock by about 10 min. These results agree to the theoretical models according to which the atmospheric disturbance propagates in a narrow cone of zenith angles up to ionospheric heights and then diverges in the form of a spherical wave with a radial velocity close to the speed of sound at these altitudes.

Received 2 December 2004; revised 6 September 2005; accepted 4 October 2005; published 20 January 2006.

Keywords: Earthquake; Acoustic gravity waves; Ionospheric irregularities.

Index Terms: 7215 Seismology: Earthquake source observations; 7851 Space Plasma Physics: Shock waves; 2439 Ionosphere: Ionospheric irregularities.