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| Titel |
Ionospheric phenomena before strong earthquakes |
| VerfasserIn |
A. S. Silina, E. V. Liperovskaya, V. A. Liperovsky, C.-V. Meister |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1561-8633
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| Digitales Dokument |
URL |
| Erschienen |
In: Natural Hazards and Earth System Science ; 1, no. 3 ; Nr. 1, no. 3, S.113-118 |
| Datensatznummer |
250000177
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| Publikation (Nr.) |
 copernicus.org/nhess-1-113-2001.pdf |
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| Zusammenfassung |
| A statistical
analysis of several ionospheric parameters before earthquakes with
magnitude M > 5.5 located less than 500 km from an ionospheric
vertical sounding station is performed. Ionospheric effects preceding
"deep" (depth h > 33 km) and "crust" (h <
33 km) earthquakes were analysed separately. Data of nighttime
measurements of the critical frequencies foF2 and foEs, the
frequency fbEs and Es-spread at the middle latitude station
Dushanbe were used. The frequencies foF2 and fbEs are
proportional to the square root of the ionization density at heights of
300 km and 100 km, respectively. It is shown that two days before the
earthquakes the values of foF2 averaged over the morning hours
(00:00 LT–06:00 LT) and of fbEs averaged over the nighttime hours
(18:00 LT–06:00 LT) decrease; the effect is stronger for the
"deep" earthquakes. Analysing the coefficient of
semitransparency which characterizes the degree of small-scale turbulence,
it was shown that this value increases 1–4 days before "crust"
earthquakes, and it does not change before "deep" earthquakes.
Studying Es-spread which manifests itself as diffuse Es track on ionograms
and characterizes the degree of large-scale turbulence, it was found that
the number of Es-spread observations increases 1–3 days before the
earthquakes; for "deep" earthquakes the effect is more
intensive. Thus it may be concluded that different mechanisms of energy
transfer from the region of earthquake preparation to the ionosphere occur
for "deep" and "crust" events. |
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