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| Titel |
The effect of earth tides as observed in seismo-electromagnetic precursory signals |
| VerfasserIn |
M. Hayakawa, Y. Sue, 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 ; 9, no. 5 ; Nr. 9, no. 5 (2009-10-27), S.1733-1741 |
| Datensatznummer |
250006994
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| Publikation (Nr.) |
 copernicus.org/nhess-9-1733-2009.pdf |
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| Zusammenfassung |
| Studies on the effect of earth tides in triggering earthquakes (EQs) had a
great progress in recent years, which has provided convincing evidence of
earth tides in EQ triggering. On the other hand, there have been accumulated
a lot of evidences on the presence of seismogenic electromagnetic effects
(such as ULF electromagnetic emissions from the lithosphere, ionospheric
perturbations as detected by subionospheric VLF/LF propagation, etc.). Since
the initial agent of these seismogenic electromagnetic effects is obviously
due to some mechanical action around the EQ focal zone, the tidal effect as
seen in EQ sequence should appear also in seismo-electromagnetic phenomena.
Based on this expectation we have studied the tidal effect in different
seismogenic phenomena, and have found that lithospheric ULF emissions exhibit
a clear maximum-minimum-maximum pattern synchronized with the lunar phase of
the EQ during several months before the EQ. As for VLF/LF propagation anomaly
representing the lower ionospheric perturbation, we have found the tidal
modulation very similar to ULF emissions, but less clear, and also there are
some differences from the ULF case (such as occasional shift with respect to
the lunar phase and/or the presence of higher frequency modulation, etc.).
These findings are indicative that those electromagnetic phenomena reported
to be in possible association with an EQ are really related with any
preparatory phase of an EQ. This kind of study would be a bridge between the
seismology and our seismo-electromagnetic study. |
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