GNGTS 2013 - Atti del 32° Convegno Nazionale

slight intensity increase at about 3.5 and 1.5 hours before the earthquake. The entire spot appeared for more than four hours, being three hours earlier than the shock time and one hour after it. The analysis of the past days and years from the same station have shown a normal behaviour for this region of the spectra. It resulted being modulated by the day/night phase. A second less apparent intensity increment of the power spectra started slightly earlier than the first one and probably went on after the first ended. It consisted of a set of narrow yellow vertical lines, which seemed to intensify at two times. These two times slightly anticipated the maximums of the first anomaly. These vertical lines had power spectra of about 5 dB above the noise level, even if their density increased at two different times. The frequency band covered nearly all of the LF spectrum, from about 30 kHz to about 90 kHz. Under 30 kHz, it became difficult to observe the density increment in the band, because it resulted being uniform over the entire recording. The maximum density increment occurred about 3.5 hours before the shock, slightly before the VLF intensification and LF spot maximums, and lasted for about one and half hours. As for the previous observation, the analysis of the past days and years from the same station have shown a normal behavior for this region of the spectra. It also resulted being modulated by the day/night phase. Conclusions. Unlike past works, the CIEN records here discussed show at least two genuine electromagnetic emissions in ELF band, which could not had been realistically produced by anthropic activities. In fact, the standing wave modulations in VLF and LF were linked to anthropic emissions from transmitters. VLF and LF transmitter carrier waves showed several gaps hours before the shock, corresponding to the sub-ionospheric channel which exactly overhangs the earthquake epicenter. Moreover, one recording in ELF band was made by a new instrument for electric charges and this was the first time it had been recorded before an earthquake. Its origin remains unclear and needs to be further investigated, even if time of occurrence appeared to have been strictly associated with the July 21, 2013 Ancona earthquake. The natural emissions having frequency ranges between 50 and 90 kHz were observed many other times from the Chieti Station. They were characterised by long lived spot and many sparks. These signals are normal variations of the ionosphere which resulted being modulated by the day/night phase. Acknowledgements. The Authors would like to gratefully thank Tommaso Cecci (ARI Città di Castello), Diego Valeri, Andrea Romualdi, Arianna Cannella and the Region of Umbria, for their observations and contribution to the realization of the CIEN stations. References de Liso,G.; Fidani, C. and Viotto, A.; 2013: Unusual Animal Behaviour before Earthquakes and Multiple Parameter Monitoring in Western Piedmont. Animals, accepted, 2013. Fidani, C.; 2010: The earthquake lights (EQL) of the 6 April 2009 Aquila earthquake, in Central Italy, Nat. Hazards Earth Syst. Sci., 10, 967-978. Fidani, C.; 2011: The Central Italy Electromagnetic Network and the 2009 L’Aquila earthquake: observed increases in anomalies. Geosciences, 1, 3-25, 2012. Loudet, L.; VLF Stations List; STD Monitoring Station: France, 2011. Available online: http://sidstation.loudet.org/ stations-list-en.xhtml (accessed on 1 November 2011). 70 GNGTS 2013 S essione 2.1