Application of radio translucence method for the ionospheric foreshock detection 
 
V.M. Smirnov, E.V. Smirnova 
 
Institute of a Radioengineering and Electronics of the Russian Academy of 
Sciences 
141190, Fryazino, sq. B.A. Vvedenskogo, 1 
vsmirnov@ire.rssi.ru 
 
Difficulties in the identification of the ionospheric perturbations caused by 
seismic effects on the background of existential variability of the ionosphere, 
especially during electromagnetic perturbances, are main object of criticism in 
the use of the ionosphere as a foreshock detector. Variations of the electronic 
density of the ionosphere interpreted as ionospheric precursors of strong 
earthquakes have the same order of size and sometimes even a smaller one on 
amplitude than the variations connected with the ionosphere fluctuations. 
However, intensive studies during the last several years have shown, that the 
seismic phenomena are unique among other reasons of the variability of the 
ionosphere. 
The process of the earthquake preparation takes, as a rule, a significant period 
of time and consequently requires carrying out long observations above the 
possible earthquake focus. The existing network of ground navigating stations 
allows carrying out such observations of the state of the ionosphere. It also 
enables us to determine the ionospheric effects of the earthquakes based on the 
analysis of an electron density of F2 layer. 
The application of global navigating satellite systems together with the methods 
of the solution of return radio translucence tasks allow to do long and regular 
measurements, which enable to investigate the temporary and spatial regularities 
occurring in the Earth ionosphere. Received as a result of the inversion of 
navigating measurements the high-altitude profiles of the distribution of the 
electron concentration can form a basis for studying such existential 
regularities of the ionosphere. 
On the basis of the results of data processing received with the use of 
navigating systems, it has been confirmed that above an epicenter of the future 
earthquake there is an infringement of an existential course of electron 
concentration of the ionosphere in F2 layer. Such modification of the profile is 
observed some day (1-3) before a forthcoming event. 
It is shown that on the basis of the analysis of the existential structure of a 
electron concentration it is possible to predict a site of a future epicenter of 
an earthquake.