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| Titel |
Spectral-decomposition techniques for the identification of periodic and anomalous phenomena in radon time-series |
| VerfasserIn |
R. G. M. Crockett, F. Perrier, P. Richon |
| 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 ; 10, no. 3 ; Nr. 10, no. 3 (2010-03-24), S.559-564 |
| Datensatznummer |
250008011
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| Publikation (Nr.) |
 copernicus.org/nhess-10-559-2010.pdf |
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| Zusammenfassung |
Two hourly-sampled time-series of soil-gas radon concentrations of durations
of the order of a year have been investigated for periodic and anomalous
phenomena. These time-series have been recorded in locations having little
or no routine human behaviour and thus are effectively free of significant
anthropogenic influences. One measurement site, Sur-Frêtes, is located
in the French Alps, with saturated soil conditions; the second site,
Syabru-Bensi, is located in Nepal, in a river terrace with unsaturated soil
conditions. In such conditions, periodic components with periods ranging
from 8 h to 7 days are often weak and intermittent and therefore, even
in the presence of stationary forcing, difficult to identify.
Two spectral decomposition techniques, Empirical Mode Decomposition (EMD) and
Singular Spectrum Analysis (SSA), have been applied to these time series and
yield similar results. For Sur-Frêtes, weak diurnal and semi-diurnal
components are observed with EMD, while SSA reveals only a diurnal
component. In Syabru-Bensi, both EMD and SSA reveal a strong diurnal
component and a weaker semi-diurnal component. Tidal components M1 and M2
are also suggested by EMD in Sur-Frêtes, while these frequencies are not
observed in Syabru-Bensi. The development of such analytical techniques can
help in characterising the multiple physical processes contributing to the
surface and subsurface dynamics of soil gases. |
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