Some dynamical characteristics of microseism time-series

ISSN： 0956-540X

Source： Geophysical Journal International, Vol.149, Iss.3, 2002-06, pp. : 589-598

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Abstract

SummaryMicroseism time-series are non-stationary, non-linear and stochastic, and these characteristics can be reproduced by a forced non-linear damped oscillator. In the present study we show that such an oscillator is also able to explain other widely observed features, such as the variation, for a given seismic station, of the frequency of the secondary peak; the variation of the frequency of the primary peak for different seismic stations relative to the same source; the variations of amplitude of the power spectrum for stormy days with respect to quiet days; and the incoherent propagation of microseisms. Numerical simulations with the proposed phenomenological model suggest i) that the main spectral peak may be due to a competitive process between the resonant response of the medium and an external harmonic force (Longuet–Higgins model), ii) that the secondary peak may be generated by the process associated with the activity of the coastal waves or as a subharmonic of the resonant frequency and iii) that the large amplitude variations between quiet and stormy days refers in fact to variations in the source (storm) distance. From a general point of view we can say microseism activity can be interpreted as the resonant response of the Earth to atmospheric cyclonic storms coupled with the oceans.