Physical interpretation and numerical modeling of the ionospheric earthquake precursors
The paper presents the results of the investigation of the anomalous ionospheric TEC variations as preearthquake signatures for the strong shock seismic events (of the magnitude M5 or larger). The hypothesis has been set that the vertical drift of the F2-layer ionospheric plasma under influence of the zonal electric field of presumably seismic origin has been the main reason for the observed disturbances in the TEC. This hypothesis has been checked by means of numerical modeling with the global 3D time-dependent Upper Atmosphere Model. Two kinds (dipolelike and monopole-like) of the presumably seismic electric field sources have been taken into consideration. The simulated results have been compared with the GPS TEC observational data for the Kithira (Source Greece) earthquake of January 8, 2008 (M6.8). It has been shown that the effects from the dipole-like electric field sources agreed well with the observations whereas monopole-like (positive) sources do not reproduce some features and underestimate the magnitude.