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| Titel |
Midnight variations of Es-spread in the ionosphere before earthquakes |
| VerfasserIn |
Elena V. Liperovskaya, Alexandra S. Silina, Victor A. Liperovsky, Claudia-Veronika Meister |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250047343
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| Zusammenfassung |
| In the present work ionospheric effects before earthquakes with magnitudes M > 4.0 are
studied. Es-spread data are analysed, which are observed every 15 minutes by the vertical
ionospheric radar stations in Petropavlovsk-Kamchatsky and Middle Asia. Considered is the
mean probability of Es-spread observation at different fbEs frequencies. The Es-spread
dependence on the season and the year of the 11-years solar activity cycle are studied.
Investigating the seismo-ionospheric effects, days with increased solar and geomagnetic
disturbances are neglected.
The analysis shows that about 1-3 days before earthquakes with depths H < 80
km appearing at midnight, the frequency of occurrence of Es-spread increases,
which indicates a strengthening of the E-layer turbulization. Es-spread is most often
observed when the distance R between epicenter and radar station is not larger than
the sum of 150 km and dimension Ro of seismic earthquake preparation region
described by the Dobrovolskyi formula, Ro = exp(M) km, R -¤ Ro + 150Â km. For
earthquakes with epicentres at larger distances and seismic shocks with deeper epicentres
no midnight effect is observed. The authors suggest that the Es-spread may be
caused in the sporadic layers by acoustic waves with periods between 20 s and
5 min, and maximum acoustic disturbances caused by phenomena at the earth’s
surface should occur at an almost vertical wave propagation. It is mentioned that the
turbulization of the E- and F-layers before earthquakes do not occur at the same time. |
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