Natural Hazards and Earth System Science www.nat-hazards-earth-syst-sci.net 1561-8633 1684-9981 10 6 2010 10.5194/nhess-10-1197-2010 http://www.nat-hazards-earth-syst-sci.net/10/1197/2010/ http://www.nat-hazards-earth-syst-sci.net/10/1197/2010/nhess-10-1197-2010.html http://www.nat-hazards-earth-syst-sci.net/10/1197/2010/nhess-10-1197-2010.pdf 1197 1208 2010-06-17 Ionospheric transients observed at mid-latitudes prior to earthquake activity in Central Italy P. Nenovski pnenovski@geophys.bas.bg Ch. Spassov M. Pezzopane U. Villante M. Vellante M. Serafimova Geophysical Institute, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy Dipartimento di Fisica, Università dell'Aquila, L'Aquila, Italy Consorzio Area di Ricerca in Astrogeofisica, L'Aquila, Italy Ionograms from Rome (41.8N, 12.5E) and Sofia (42.4N, 23.2E) ionospheric stations during earthquake (EQ) activity with magnitude (<i>M</i>) between 5 and 6 in Central Italy are analyzed. It is found that several ionospheric disturbances occur in the intermediate E-F region before the EQ shock. In fact, besides sporadic E (Es) layer development (of type h) of short duration (transients), fmin increase, trace gaps near the critical frequencies, and E region trace disappearance are also observed within one to three hours before the EQ shock. Before the EQ shocks we find that the F2 region parameters are practically undisturbed. 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