Maximal Lyapunov exponent variations of volcanic tremor recorded during explosive and effusive activity at Mt Semeru volcano, Indonesia

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Title:	Maximal Lyapunov exponent variations of volcanic tremor recorded during explosive and effusive activity at Mt Semeru volcano, Indonesia
Authors:	柯士達;Konstantinou, K. I.;Perwita, C. A.;Maryanto, S.;Budianto, A.;Hendrasto, M.
Contributors:	地球科學學院地球科學學系
Keywords:	Chaos theory;Dynamical systems;Explosions;Fluid flow;Fluid pressure;Frequencies;Geophysics;Lyapunov exponents;Magma;Mathematical models;Nonlinearity;Pressure;Tremors;Volcanoes
Date:	2013-12-23
Issue Date:	2026-04-23 11:37:36 (UTC+8)
Publisher:	European Geosciences Union;Gottingen: Copernicus GmbH
Abstract:	摘要： Abstract. 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. 出版者： Gottingen: Copernicus GmbH 出版日期： 2013-12-23 出處： Nonlinear Processes in Geophysics, 2013-12, Vol.20 (6), p.1137-1145 資源來源： Publicly Available Content Database 版權： Copyright American Geophysical Union Nov 2013 識別號： ISSN: 1607-7946 識別號： ISSN: 1023-5809 識別號： EISSN: 1607-7946 識別號： DOI: 10.5194/npg-20-1137-2013
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