Viable precursors of paroxysmal phenomena as detected by applying RQA to Acoustic Emission time series

Recurrence quantification analysis (RQA) represents a recent method for processing nonlinear time series, already addressed to different topics concerning earth sciences and others. RQA is applied in this work to analyze time series of acoustic emission (AE) triggered by Earth's crust phenomena, so to detect feasible precursors of catastrophic events. The AE records of rms values were acquired at two different sites, placed close to the Peteroa volcano (Argentina) and at Valsinni (Matera, Italy), considering two ultrasound frequencies (25 and 150 kHz) with 30-sec sampling rate. The preliminary results of the application of RQA to the AE data of Valsinni with respect to the L'Aquila earthquake (Italy, on April 6, 2009), and to those related to the activity of the Peteroa volcano (Argentina) are described and appear suited to stress relationships with an impending catastrophic event.