Main phenomenological features of ionospheric precursors of strong earthquakes |
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| Authors: | S A Pulinets A D Legen'ka T V Gaivoronskaya V Kh Depuev |
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| Institution: | a Instituto de Geofísica, UNAM, Ciudad Universitaria, Delegación de Coyoacán, 04510, México D.F., Mexico;b Institute of Terrestrial Magnetism, Ionosphere and Radiowave Propagation, Russian Academy of Sciences (IZMIRAN), Troitsk, 142190, Moscow Region, Russia |
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| Abstract: | This paper summarizes the results of more than 10 years spent by the authors studying the variations in the ionosphere over seismically active regions several days or hours before strong earthquakes. The physical mechanisms of such variations established by the authors and published previously are submitted in the references. This article is aimed mainly at determining the major characteristic parameters of the observed effects (temporal and spatial variations, range in amplitude, etc.) to provide the means to separate the seismogenic effects from other forms of ionospheric variability. Data obtained by ground-based ionosondes and by topside vertical sounding from satellites are used in conjunction with local probe measurements. The topside vertical profiles of the electron concentration are analyzed. It is shown that the most characteristic effect is that of scale height changes in the vertical distribution of ions and electrons implying a decrease in the mean ion mass within the F-layer due to seismogenic effects. This result is supported by direct mass-spectrometer measurements. Differences between magnetic storm ionospheric disturbances and seismogenic variations within the ionosphere are also discussed. |
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