Localization of the source of ionospheric disturbance generated during an earthquake

Abstract

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 F 2 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.

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

“…The size of this area is very small and close to a characteristic size of the first Fresnel zone radius (3-4 km for 5.26 MHz). Meantime, TEC variations show changes within the region of the main maximum of electron concentration with a characteristic size of the order of 100-300 km (Afraimovich et al, 2003(Afraimovich et al, , 2004a(Afraimovich et al, , 2005(Afraimovich et al, , 2006. Therefore, the duration of HF Doppler shift response during wavepacket propagation is less than the duration of TEC perturbation (Afraimovich et al, 2004b).…”

“…The parameters of TEC response to SAW, excited by the main shock of the earthquake, agree well with the results of earlier papers devoted to the study of ionospheric effects of earthquakes. Such ionospheric disturbances propagate no further than 1000 km with a velocity of about 1000 m/s (Calais and Minster, 1995;Afraimovich et al, 2001aAfraimovich et al, , 2002Afraimovich et al, , 2005Afraimovich et al, , 2006Heki and Ping, 2005).…”

“…Many publications have been devoted to the study of the ionospheric response to strong earthquakes (Davies and Baker, 1965;Tanaka et al, 1984;Liu et al, 2006;Calais and Minster, 1995;Afraimovich et al, 2001aAfraimovich et al, , 2002Afraimovich et al, , 2005Afraimovich et al, , 2006Ducic et al, 2003;Heki and Ping, 2005). Atmospheric waves excited by earthquakes include several types of waves (Pokhotelov et al, 1995;Ducic et al, 2003;Artru et al, 2004;Heki and Ping, 2005) and manifest themselves in the ionosphere as traveling ionospheric disturbances (TIDs).…”

Near-field TEC response to the main shock of the 2008 Wenchuan earthquake

“…It is very interesting to compare the obtained characteristics of the TEC response to the Wenchuan earthquake with similar parameters for other strong earthquakes (Afraimovich et al, 2001a(Afraimovich et al, , 2006Ducic et al, 2003;Heki et al, 2006;Otsuka et al, 2006;Kiryushkin and Afraimovich, 2007). General information about these earthquakes is presented in left part of Table 1 (including the time of the main shock in the universal time UT, the position of the earthquake epicenter, depth, the magnitude, as well as the level of geomagnetic disturbance from the data on D stvariations).…”

“…On the basis of this concept the different methods of space-time processing of TEC series were developed, including quasi-optimum algorithm, QOA (Afraimovich et al, 2002(Afraimovich et al, , 2006Kiryushkin and Afraimovich, 2007). These algorithms realized the coherent summation of the TEC series accounting for space-time parameters of disturbance.…”