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Authors: | De Lauro, E.* Falanga, M.* Petrosino, S.* |
Title: | Study on the Long-Period source mechanism at Campi Flegrei (Italy) | Journal: | Physics of the Earth and Planetary Interiors | Series/Report no.: | /206-207 (2012) | Publisher: | Elsevier Science Limited | Issue Date: | 7-Jul-2012 | DOI: | 10.1016/j.pepi.2012.06.006, | URL: | http://www.sciencedirect.com/science/article/pii/S0031920112001100 | Keywords: | Lp sources Poissonian occurrence Tidal modulation |
Subject Classification: | 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology | Abstract: | The source properties of the Long-Period events that occurred at Campi Flegrei Caldera (Italy) during the 2004–2006 ground uplift episode are investigated by analyzing the temporal release of seismic energy, amplitude distribution and inter-event occurrence time. Moreover, an entropy-based decomposition method is applied to identify the simpler waveforms thought to be representative of the source mechanism of Long-Period events. On the basis of the outcomes, we propose that the main part of these events is the result of a source process triggered by a mechanism of fluid charge/discharge, which causes pressure drop in a main branch of a dentritic network of the hydrothermal system. In this model, the rate of the Poissonian process (about 15 min), which drives the occurrence of the Long-Period events, provides the average recharge time of the system up to the critical condition. A partial shunting of the fluid flow away from the main conduit activates the ”resonance” of a second branch, spatially separated from the first one. This is a process that occurs whenever the fluid pressure exceeds a critical value and produces less energetic Long-Period events. The mechanism of pressure variation in the two conduits generates signals with preferred amplitude scales, described by a bi-lognormal distribution. From a dynamical point of view, Long-Period events result well described by a low-dimensional dynamical system. Finally, the time pattern of the energy release and its correlation with the diurnal solid earth tide suggest that the whole mechanism of fluid charge/discharge is likely modulated by tidal stress variation. |
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