P. M. Siciliani 1, C. Fidani 1,2, F. Stoppa 3, G. Iezzi 3, M. Arcaleni 1, S. Tardioli 1, D. Marcelli 2 1

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1 Electromagnetic perturbations associated with M = 5, July 21, 2013, Ancona, Italy earthquake observed by CIEN P. M. Siciliani 1, C. Fidani 1,2, F. Stoppa 3, G. Iezzi 3, M. Arcaleni 1, S. Tardioli 1, D. Marcelli 2 1 Osservatorio Sismico A. Bina, Perugia, Italy 2 Central Italy Electromagnetic Network, San Procolo, Italy 3 Dipartimento di Scienze della Terra, U.d A., Chieti, Italy Introduction. Two new CIEN stations have been recently installed in the Umbria Region: in Avigliano Umbro and Città di Castello. These two new stations have same features as the nine preexisting stations. So, currently there are 11 stations continuously recording electric fields, see Fig. 1. The two new stations had already been activated by July 21, 2013, when a strong earthquake, M w = 5, struck in the Adriatic Sea a few kilometers from the shore under Monte Conero near the city of Ancona. The monitored electric signals ranged from ELF (4 Hz 1 khz) to LF (25 khz 100 khz) bands (Fidani, 2011). Three stations were not recording at that time: Siena, Città di Castello and Capitignano. According to reports received by EMSC, the main shock occurred at 01:32 UTC (local time Sunday, July 21, 2013 at 03:32) and lasted for seconds. The depth of the shock was reported as 5 km, near the villages of Numana and Sirolo, Ancona Province. No damage or injury was reported. Two probable macro anomalies were collected from the population. One earthquake light (Fidani, 2010) was observed hours before the shock by two witnesses. It was reported as a ball of light positioned toward the south, at about 00:00-00:30 LT 21 July That morning, the witnesses were traveling by car from the south of Ancona towards Loreto along the highway when they saw a light from behind a hill in the west. It was bigger than a 66

2 street light but smaller than the Moon. This luminous sphere was a faded white color. This light quickly moved from the west to the east, forming an arc downwards and disappearing behind houses. This event lasted 2 seconds. Furthermore, gas bubbles appeared in the sea around the port of Numana days after the quake. From 2011, the necessity to better understand the sources of some signals has been supported by the idea that a number of different measurements at each CIEN site should be increased. Thus, the Fermo and Torre Pellice Stations have been recently equipped with Geiger counters for atmospheric radioactivity, as well as meteorological stations which record temperature, humidity, wind speed and direction, atmospheric pressure and rainfall. The Fermo Station has also been equipped with an underground thermometer to measure ground temperature and an LF radio receiver at 150 khz to record amplitude modulation. The Torre Pellice Station had already been equipped with a magnetometer, a Radon meter and a compass to check the direction of the geomagnetic field. Recently, this station has been equipped with an sub-sound detector to investigate for the origin of animal responses to earthquakes (De Liso, 2013). The Perugia Station has been recently equipped with a new electromagnetic sensor, sensitive to electric charges and vertical electric fields. The same station has always measured for meteorological parameters and seismological activity through the A. Bina Observatory. ELF observations. An example signal, recorded by the N-S antenna in Avigliano Umbro on July 19, 2013, at about 1:00LT, is shown in Fig. 2 on the left. Its oscillation covers a similar frequency range as those already reported in other publications (Fidani, 2011); between 50 and 100 Hz. Moreover, the duration of the signal was about 7 min, as well, other traces of it appeared hours before and after it. The frequencies of these signals increased at the beginning, but decreased towards the end. However, no time correspondence was observed between the signals recorded at all of the stations, indicating that they were of local origin. Additionally, their times did not coincide with the earthquake time. Moreover, the signatures almost always appeared on only one antenna of each station and when appearing on both antennas, the two signatures were always different. Strong ELF signals were also recorded by the Fermo and Perugia Stations during the weeks prior to the July 21, 2013, Ancona earthquake. These oscillations had frequencies ranging between 40 and 200 Hz, they also often started and ended at lower frequencies. Moreover, the durations of the signals ranged from few minutes to several hours. The strongest intensities were recorded on the days before and after the main shock, with amplitudes greater than 1 μv/m. Fig. 1 The positions of the 11 CIEN stations are indicated by small red circles and the Ancona, July 21, 2013, M w = 5, earthquake epicenter is indicated by a yellow circle. 67

3 A new type of sensor has been recently installed at the Perugia Station, that measures air and rain electricity, along with vertical electric fields. It was activated on the top of the A. Bina Observatory at the beginning of April, It recorded a clear signal from about 30 minutes to 5 minutes before the Ancona shock, then the signal suddenly disappeared, see Fig. 2 on the right. The new sensor recorded an electric oscillation which had probably stated under 10 Hz and increased up to 200 Hz, with a frequency width of about 50 Hz. The electric vibration power intensity reached a signal to noise ratio of about db in the Hz range. Disappearing, the signal covered the whole range of Hz in a few seconds. VLF observations. VLF signals from transmitters (Loudet, 2011) in Novosibirsk, Krasnodar and Khabarovsk, Russia of the Alpha 500 kw radio navigation system, at khz, khz and khz; 400 kw in Rosnay, France at 15.1 khz and khz; 100 kw in Matotchkinchar, Russia at 18.1 khz; 400 kw in Anthorn/Skelton, England at 19.6 khz and 22.1 khz; 400 kw in Saint-Assise, France at 20.9 khz; 800 kw in Rhauderfehn, Germany at 23.4 khz; 1,000 kw in Culter, Maine at 24.0 khz and 192 kw in Seattle, Washington at 24.6 khz, were analysed from the Fermo, Chieti and Perugia Stations before and after the shock time, to verify if any signals had had a depletion in their carrier waves. Depletions appeared in the signal from Anthorn transmitter at 19.6 khz, at Fermo, Perugia and Chieti Stations, occurring hours before and after the recorded time of shock. Especially at Fermo, where the power loss was about 10 db, see Fig. 3 at the top. The sub-ionospheric channel between Fermo and Anthorn overhang the earthquake epicenter. Natural VLF signals were also monitored at this time. The vertical signatures appearing in the VLF spectrogram represent distant lightning origins, which fill a large band intensity modulate by the ionosphere altitude and diffusion, following the day/night cycle. The intensity of this band is modulated by lightning activity, and its frequencies are also selected by the ionosphere altitude and diffusion. An increased activity was observed in the band intensity hours before the earthquake, showing two maximums, at the Fermo, Chieti and Perugia Stations. However this variation was completely normal following the long time observation of the frequency band. It might have been due to normal ionospheric fluctuations. LF observations. The Fermo, Torre Pellice and Chieti Stations had already been modified to produce LF spectrogram (Fidani, 2011): Fermo and Torre Pellice Stations from 25 khz to 50 khz while the Chieti Station from 25 khz to 100 khz. Specifically, the Chieti Station receives LF signals from (Loudet, 2011): Bafa, Turkey, 26.7 khz; Kaliningrad, Russia, 30.3 khz; Niscemi, Italy, 45.9 khz; Maraton, Greece, 49.0 khz; Irkutsk, Russia, 50.0 khz; Anthorn, England, 60.0 khz; La Règine, France, 62.6 khz; Kerlouan, France, 65.8 khz; Moscow, Russia, 66.6 khz; Lintong, China, 68.5 khz; Prangings, Switzerland, 75.0 khz; Mainflingen, Fig. 2 The ELF signals recorded at the Avigliano Umbro Station on July 19, 2013, N-S antenna, on the left; the electric signal observed by the new instrument at the Perugia Station a few minutes before the shock. 68

4 GNGTS 2013 Sessione 2.1 Germany, 77.5 khz; Inskip, England, 81.0 khz. Considering also transmitters in VLF band, monitoring reaches a total of 21 transmitters, from all directions around the station. Strong attenuations appeared in the carrier wave of a LF transmitters at the Chieti Station, whereas exaltations appeared in another carrier wave, no noise reduction was recorded for the rest of the bands at the same time. Additionally, no attenuation was observed for all of the other carrier wave transmitters at the same times. Depletions appeared in the signal from Mainflingen while exaltations from an unknown transmitter at 87 khz, both occurring hours before the recorded time of shock, see Fig. 3 at the bottom. The sub-ionospheric channel between Chieti and Mainflingen exactly overhang the earthquake epicenter. Opposed amplitude phases between the two carrier waves also appeared. In this case, power spectral attenuations exceeded 20 db up to 30 db under the normal power intensity level. The other LF carrier waves from all three CIEN stations were stable in intensity. A slight depletion from the Maraton transmitter began and ended hours before the Ancona quake at the Fermo Station, see Fig. 3 at the top, the power loss was about 5 db. Finally, the sub-ionospheric channel between Fermo and Maraton does not overhang the earthquake epicenter. Two kinds of spectrum perturbations were observed in the Chieti recordings hours before and after the Ancona earthquake, see Fig. 3 on the top. The most striking perturbation began near 23:00 LT on July 20, 2013, when a power spectra increased about 5 db between 85 and 95 khz, reaching about 10 db above the normal noise level at two different times before the quake. About one hour after the shock, this perturbation disappeared. The LF increased power intensity distribution formed a spot similar to an electromagnetic noise, which presented a Fig. 3 VLF and LF spectrograms recorded between 22:30 on July 20 and 04:30 on July 21, 2013, VLF at the Fermo Station at the top and LF at the Chieti Station at the bottom; the vertical black line indicates the earthquake time. 69

5 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, Fidani, C.; 2010: The earthquake lights (EQL) of the 6 April 2009 Aquila earthquake, in Central Italy, Nat. Hazards Earth Syst. Sci., 10, Fidani, C.; 2011: The Central Italy Electromagnetic Network and the 2009 L Aquila earthquake: observed increases in anomalies. Geosciences, 1, 3-25, Loudet, L.; VLF Stations List; STD Monitoring Station: France, Available online: stations-list-en.xhtml (accessed on 1 November 2011). 70