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www.nat-hazards-earth-syst-sci.net/9/53/2009/
doi:10.5194/nhess-9-53-2009
© Author(s) 2009. This work is distributed
under the Creative Commons Attribution 3.0 License.
Day-time variations of foF2 connected to strong earthquakes
1Institute of Physics of the Earth of the Russian Academy of Sciences, Bolshaya Gruzinskaya 10, 123995 Moscow, Russia
2Institute of Cosmophysical Research and Radio Wave Propagation, Far Eastern Branch of the Russian Academy of Sciences, 684034 Petropavlovsk-Kamchatsky, Russia
3Physics Department, University of Bari, 70126 Bari, Italy
4Technische Universität Darmstadt, Institut für Kernphysik, Schlossgartenstr. 9, 64289 Darmstadt, Germany
5Geophysical Centre of the Russian Academy of Sciences, Molodejnaya 3, 117296 Moscow, Russia
Abstract. The statistical analysis of the characteristic frequency foF2 of the Earth's ionosphere averaged over mid-day hours – from 11:00 till 17:00 h LT – is carried out. Disturbances of foF2 connected to earthquakes are considered on the background of seasonal, geomagnetic, 11-years and 27-days solar variations. A special normalized parameter F is introduced, which represents the almost seasonal-independent part of foF2. Days with high solar (Wolf number >100) and geomagnetic (∑Kp>30) activity are excluded from the analysis. Events with magnitude M>5, distance from the sounding station R<500 km and depth h<70 km are taken into account. The superimposed epoches' method is used to determine the temporal dependence of F. It is found that F increases about 3–6 days before the earthquakes and then decreases one day – two days before the shock. The decreased values of F continue to exist two-three days after events with M>5.5. The obtained phenomenon depends on the magnitude of the earthquake. For events with M>5.5, the reliability of the effect is larger than 95%. For data of more than 80 earthquakes in the vicinity of Petropavlovsk-Kamchatsky and more than 200 earthquakes in the vicinity of Tokyo analogous results are obtained.
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Citation: Liperovskaya, E. V., Bogdanov, V. V., Biagi, P.-F., Meister, C.-V., Liperovsky, V. A., and Rodkin, M. V.: Day-time variations of foF2 connected to strong earthquakes, Nat. Hazards Earth Syst. Sci., 9, 53-59, doi:10.5194/nhess-9-53-2009, 2009. Bibtex EndNote Reference Manager XML
