Interaction between seismicity and deformation on different time scales in volcanic areas: Campi Flegrei and Stromboli

摘要

Abstract. We study oscillations recorded at Stromboli and Campi Flegrei by different sensors: seismometers, strainmeters and tiltmeters. We examine both the high-frequency (0.5Hz) portion of the spectrum and very long period signals up to tidal scales. In this context, seismicity and deformation are investigated on different time scales (from minutes to days/years) in order to identify the basic elements of their interaction, whose understanding should provide new insights on the predictive models. In this work, the strict relation of tides and volcanic processes is shown. At Stromboli, indeed the transition from the stationary phase to the non-stationary phase seems to have a tidal precursor that is related to theduration of the crisis. The subsequent volcanic activity is interpreted asthe response of the volcano to restore the equilibrium condition. The moveout from equilibrium produces, first, variations in the standard statistics of explosions, then leads to effusive stage and to a pressuredrop in the shallow feeding system. That process induces the nucleation of agas bubble and the excitation of low frequencies. Campi Flegrei seismicityshows a correlation between the diurnal solar solid tide and the energyreleased by the long period signals, indicating that the whole mechanism ismodulated on a tidal scale. In other words, in the case of Stromboli, adeparture from the equilibrium state is marked by solid tide variations in acertain frequency band. On the other hand, at Campi Flegrei diurnal toannual solid tides modulate an increase of volcanic activity.