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| Titel |
Maximal Lyapunov exponent variations of volcanic tremor recorded during explosive and effusive activity at Mt Semeru volcano, Indonesia |
| VerfasserIn |
K. I. Konstantinou, C. A. Perwita, S. Maryanto, A. Budianto, M. Hendrasto |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1023-5809
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| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 20, no. 6 ; Nr. 20, no. 6 (2013-12-23), S.1137-1145 |
| Datensatznummer |
250086085
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| Publikation (Nr.) |
 copernicus.org/npg-20-1137-2013.pdf |
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| Zusammenfassung |
| We analyze 25 episodes of volcanic tremor recorded from 22 November until
31 December 2009 at Mt Semeru volcano in order to
investigate their spectral and dynamical properties. The overtone frequencies
for most of the tremor events indicate a pattern of period-doubling, which is
one possible route that can lead a system to chaotic behavior. Exponential
divergence of the phase space orbits is a strong indicator of chaos and was
quantified by estimating the maximal Lyapunov exponent (MLE) for all tremor
events. MLEs were found to vary linearly with the number of frequency
overtones present in the tremor signals. This implies that the tremor source
at Semeru fluctuates between a quasi-periodic state with few overtone
frequencies (2–3) and small MLEs (~0.013), and a chaotic one
with more overtones (up to 8) and larger MLEs (up to 0.039). These results
agree well with the tremor generation model suggested previously by Julian
(1994), which describes wall oscillations of a crack excited by unsteady
fluid flow. In this model, as fluid pressure increases, a period-doubling
cascade leads to numerous new frequencies and a chaotic tremor signal. The
temporal variation of MLEs exhibited significant fluctuations from 23 until
31 December when the eruptive activity shifted from explosive to effusive.
Such a situation may reflect variable fluid pressure conditions inside the
conduit, where at first magma is accumulated and subsequently is erupted,
releasing the buildup of pressure. Our results give further evidence for the
role of nonlinear deterministic processes in generating volcanic tremor and
call for similar investigations to be conducted in other volcanoes. |
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