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www.nat-hazards-earth-syst-sci.net/8/1041/2008/
doi:10.5194/nhess-8-1041-2008
© Author(s) 2008. This work is distributed
under the Creative Commons Attribution 3.0 License.
Disturbances in a VLF radio signal prior the M=4.7 offshore Anzio (central Italy) earthquake on 22 August 2005
1Department of Physics, University of Bari, Via Amendola, 173 – 70126 Bari, Italy
2Inter-Department Centre for the Evaluation and Mitigation of the Volcanic and Seismic Risk, University of Bari, Italy
3Department of Engineering of Enterprise, University of Roma Tor Vergata, Via di Tor Vergata – 00133 Rome, Italy
4Department of Biomedical Sciences, University of Foggia, Via L. Pinto-71100 Foggia, Italy
5United Institute of the Earth's Physics, Russian Academy of Science, Bolshaya Gruzinskaya 10, 123995 Moscow, Russia
6Department of Electronic Engineering, The University of Electro-Communications, 1-5-1 Chofugaoka, Chofu City, Tokyo 182-8585, Japan
Abstract. On 22 August 2005 an earthquake with magnitude M=4.7 occurred in the Anzio (central Italy) offshore area. From 2002, a VLF-LF radio receiver is into operation in Bari (southern Italy). The intensity and the phase of the signals transmitted by GB (f=16 kHz, United Kingdom), FR (f=20.9 kHz, France), GE (f=23.4 kHz, Germany), IC (f=37.5 kHz, Island) and IT (f=54 kHz, Sicily, Italy) has been monitored with a 5 s sampling rate. The previous epicenter is near enough to some of the radio paths and the data collected were studied in order to reveal possible seismic effects. The raw analysis revealed a clear drop in the intensity of the FR radio signal on 19 August. Then the wavelet analysis was applied to the intensity and the phase data of the different radio signals. In the mentioned day an increase in the band 60–120 min was revealed in the spectra of the FR signal. Then the principal component analysis was applied and again the 19 August stood up as an anomalous day for the FR radio signal. The path of this signal, among the paths of the five radio signals collected by the Bari receiver, is the nearest to the mentioned epicentre and the anomaly revealed on 19 August appears as a precursor of the earthquake. This result confirms the possible precursor revealed by other researchers in the air Rn content in a site located 5 miles far from the epicenter.
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Citation: Biagi, P. F., Castellana, L., Maggipinto, T., Loiacono, D., Augelli, V., Schiavulli, L., Ermini, A., Capozzi, V., Solovieva, M. S., Rozhnoi, A. A., Molchanov, O. A., and Hayakawa, M.: Disturbances in a VLF radio signal prior the M=4.7 offshore Anzio (central Italy) earthquake on 22 August 2005, Nat. Hazards Earth Syst. Sci., 8, 1041-1048, doi:10.5194/nhess-8-1041-2008, 2008. Bibtex EndNote Reference Manager XML
