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| Titel |
On the ionospheric perturbation associated with the 2007 Niigata Chuetsu-oki earthquake, as seen from subionospheric VLF/LF network observations |
| VerfasserIn |
M. Hayakawa, T. Horie, M. Yoshida, Y. Kasahara, F. Muto, K. Ohta, T. Nakamura |
| 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 ; 8, no. 3 ; Nr. 8, no. 3 (2008-06-17), S.573-576 |
| Datensatznummer |
250005534
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| Publikation (Nr.) |
 copernicus.org/nhess-8-573-2008.pdf |
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| Zusammenfassung |
| In order to investigate any precursory effect of ionospheric perturbations
associated with the large 2007 Niigata Chuetsu-oki earthquake (16 July 2007)
(magnitude, 6.8), we have made full use of our VLF/LF network
observation in Japan by examing the four propagation paths; JJI transmitter
(Kyusyu, Ebino)-MSR (Moshiri, Hokkaido), JJY transmitter (Fukushima)-MSR,
JJY-KOC (Kochi) and JJI-CBA (Tateyama, Chiba). For the former two paths of
JJI-MSR and JJY-MSR, we have observed significant propagation anomalies
(both a decrease in nighttime average amplitude and an enhancement in
nighttime amplitude fluctuation both satisfying the 2σ (σ:
standard deviation) criteria) on 8–9 July, about one week before the
earthquake. However, the lack of observation for the path from JJY-KOC, has
enabled us to make no conclusion for this path. On the other hand, the path
from JJI-CBA does not seem to be perturbed. Although this earthquake is very
big and shallow, the amount of VLF anomaly for this earthquake is not so
pronounced as expected, probably because the epicenter is not unfortunately
located within the sensitive areas of any propagation paths. These
observational facts suggest that the lower ionosphere above the epicenter is
perturbed definitely prior to the earthquake, with radius of a few hundred
kilometers. |
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