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| Titel |
Possible earthquake precursors revealed by LF radio signals |
| VerfasserIn |
P. F. Biagi, R. Piccolo, A. Ermini, S. Martellucci, C. Bellecci, M. Hayakawa, V. Capozzi, S. P. Kingsley |
| 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 ; 1, no. 1/2 ; Nr. 1, no. 1/2, S.99-104 |
| Datensatznummer |
250000027
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| Publikation (Nr.) |
 copernicus.org/nhess-1-99-2001.pdf |
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| Zusammenfassung |
| Among radio signals,
low frequency (LF) radio signals lie in the band between 30–300 kHz.
Monitoring equipment with the ability to measure the electric strength of
such signals at field sites, were designed and assembled in Italy. From
1993 onwards, the electric field strength of the MCO (216 kHz, France)
broadcasting station has been collecting measurements at two sites in
central Italy that were chosen according to very low noise levels. At the
end of 1996, radio signals from the CLT (189 kHz, Italy) and CZE (270 kHz,
Czech Republic) broadcasting stations were included in the measurements.
Meteorological data from central Italy were also collected over the same
time period in order to study the influence of weather conditions on the
experimental measurements. During the monitoring period, we observed some
evident attenuation of the electric field strength in some of the radio
signals at some of the receivers. The duration of the attenuation observed
was several days, so it could possibly be related to particular
meteorological conditions. On the other hand, this phenomenon might
represent precursors of moderate (3.0 < M < 3.5)
earthquakes that occurred near the receivers (within 50 km) along the
transmitter-receiver path. In this case, it is possible that the
pre-seismic processes could have produced irregularities in the
troposphere, such as ducts, reflecting layers and scattering zones, so
that some local troposphere defocusing of the radio signals might have
occurred. These observations were related only to moderate earthquakes and
in these cases, suitable meteorological conditions were probably needed to
observe the effect. Between February – March 1998, we observed at one
measuring site, a significant increase in the CZE electric field strength.
Unfortunately, we could not use the data of the other receiver in this
case, due to frequent interruptions in the data set. The increase might
have been a precursor of the strong seismic sequence (M = 5.0–6.0) that
occurred during March – May 1998 in Slovenia at a location over 400 km
from the receiver, but lying in the middle of the transmitter-receiver
path. In this case, it is possible that an ionospheric disturbance,
produced by the pre-seismic processes, might have occurred. |
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