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| Titel |
VLF-LF radio signals collected at Bari (South Italy): a preliminary analysis on signal anomalies associated with earthquakes |
| VerfasserIn |
P. F. Biagi, R. Piccolo, L. Castellana, T. Maggipinto, A. Ermini, S. Martellucci, C. Bellecci, G. Perna, V. Capozzi, O. A. Molchanov, M. Hayakawa, K. Ohta |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1561-8633
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| Digitales Dokument |
URL |
| Erschienen |
In: Natural Hazards and Earth System Science ; 4, no. 5/6 ; Nr. 4, no. 5/6 (2004-11-03), S.685-689 |
| Datensatznummer |
250001385
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| Publikation (Nr.) |
 copernicus.org/nhess-4-685-2004.pdf |
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| Zusammenfassung |
| At the beginning of 2002 an OmniPAL receiver was put into operation at the
Department of Physics of Bari University (Southern Italy). The electric
field strength of five VLF-LF signals transmitted from United Kingdom (f=16kHz),
France (f=20.9kHz), Germany (f=23.4kHz), Iceland (f=37.5kHz) and Italy
(f=54kHz) has been monitoring with a 5s sampling frequency. In a first step we
reduced the amount of the data taking one datum each 10min (mean of
the ±5min raw data) and then we smoothed these data by a running adjacent
averaging over 7 days. Analysing the trends we obtained, we revealed at
first in the signal from the Italian transmitter two clear intensity
decreases in April 2002 and in August-September 2002. At these times we
observed earthquakes with M=4.3 and M=5.6 respectively near the
transmitter-receiver path and a precursory effect in the previous decreases
appeared. Then, we noted that all of the five radio trends in the time
interval March 2002-February 2003 are more disturbed than in other
periods; in particular an evident simultaneous decrease appears in
January-February 2003. We propose that these disturbances are related to
general excitation of the margin between the African and European plates. In
a second step we examined the terminator time (evening) changes for the
Italian transmitter in July-September 2002, and we found significant
deviations from the mean value at the end of August, which is supportive for
some precursory ionospheric signature of earthquakes. |
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