Stuttgart 2012 – wissenschaftliches Programm
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EP: Fachverband Extraterrestrische Physik
EP 7: Poster Erdnaher Weltraum
EP 7.9: Poster
Mittwoch, 14. März 2012, 16:30–19:00, Poster.IV
Nighttime Es-spread observations before strong earthquakes — Elena Liperovskaya1, Alexandra Silina1, Viktor Liperovsky1, •Claudia-Veronika Meister2, Dieter Hoffmann2, and Pier-Francesco Biagi3 — 1Institute of Physics of the Earth, 123995 Moscow, Russia, liper@ifz.ru — 2Technische Universität Darmstadt, 64289 Darmstadt, Germany, c.v.meister@skmail.ikp.physik.tu-darmstadt.de — 3University of Bari, 70126 Bari, Italy, biagi@fisica.uniba.it
Night-time observations of Es-spread performed every 15 minutes with the vertical ionosondes Petropavlovsk-Kamchatsky and Dushanbe before earthquakes of the magnitude M>4 are analysed. The percentage of spreading effects is found for different values of the maximum reflection frequency fbEs. The dependence of Es-spread on the season as well as the year of the 11-yr solar activity cycle is also studied.
The analysis shows that 1-3 days before seismic shocks in the Earth’s crust at depths of h<80 km, the occurrence frequency of Es-spread increases a few hours before midnight. This effect is characteristic for a strengthening of the turbulization of the E-layer plasma. It is found that Es-spread is observed more often, when the distance between the epicenter and the ionosonde is not larger than RD+150 km. RD describes the dimension of the earthquake preparatory region, which is estimated by the Dobrovolsky formula RD=exp(M) km. In cases of earthquakes at larger distances and in larger depths, the midnight-effect is not found. The authors assume that the observed Es-spread is caused by acoustic waves with periods of 20 s - 5 min.