on the ionospheric perturbation associated with the 2007 niigata chuetsu-oki earthquake, as seen from subionospheric vlf/lf network observations

Clicks: 159
ID: 154425
2008
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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hayakawa2008naturalon Use this key to autocite in the manuscript while using SciMatic Manuscript Manager or Thesis Manager
Authors ;M. Hayakawa;T. Horie;M. Yoshida;Y. Kasahara;F. Muto;K. Ohta;T. Nakamura
Journal anziam journal
Year 2008
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