 |
| Titel |
Long-range correlation and nonlinearity in geochemical time series of gas discharges from Mt. Etna, and changes with 2001 and 2002–2003 eruptions |
| VerfasserIn |
A. Paonita |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1023-5809
|
| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 17, no. 6 ; Nr. 17, no. 6 (2010-12-10), S.733-751 |
| Datensatznummer |
250013761
|
| Publikation (Nr.) |
 copernicus.org/npg-17-733-2010.pdf |
|
|
|
|
|
| Zusammenfassung |
| In this paper, spectral and detrended fluctuation analyses, as well as time
reversibility and magnitude-sign decomposition, have been applied to the
10-year time-series data resulting from geochemical monitoring of gas
emissions on the flanks of Mt. Etna, and gases from a CO2 exploitation
well located tens of kilometers from the volcano. The analysis of the time
series which showed main effects of fractionation between gases due to
selective dissolution in aquifers (e.g., the CO2 concentration series),
revealed the occurrence of random fluctuations in time, typical of systems
where several processes combine linearly. In contrast, the series of He
isotopic composition exhibited power-law behavior of the second-order
fluctuation statistics, with values of the scaling exponent close to 0.9.
When related to the spectral exponent, this value indicates that the
isotopic series closely resemble fractal flicker-noise signals having
persistent long-range correlations. The isotopic signals also displayed
asymmetry under time reversal and long-range correlation of the associated
magnitude series, therefore it was statistically proved the presence of
nonlinearity. Both long-range correlation and nonlinearity in time series
have been generally considered as distinctive features of dynamic systems
where numerous processes interact by feedback mechanisms, in accordance with
the paradigm of self-organized criticality (SOC). Thus, it is here proposed
that the system that generated the isotope series worked under conditions of
SOC. Since the fluctuations of the isotope series have been related to magma
degassing, the previous results place constraints on the dynamics of such
process, and suggest that nonequilibrium conditions must be dominant. It
remains unclear whether the signature of SOC is directly due to volatile
degassing from magma, or if it derives from the interaction between melt and
the stress field, which certainly influences magma decompression. The
strength of scaling appears to increase after 2002 (α values from
0.8 up to 1.2), focusing on transition of the Etnean system from typical SOC
toward conditions of lower criticality. By comparing this transition with
those of geophysical observables, it can be suggested that the drop in the
rate of magma supply, subsequent to the paroxysms of 2001 and 2002–2003,
was the main cause of the scaling change. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|