RQA applied to Acoustic Emissions time series to pinpoint feasible precursors of catastrophic geological events

The paper deals with a relatively new technique, the Recurrence Quantification Analysis (RQA), a non-linear time series processing approach already utilized in different disciplines such as Economy, Physiology, Neurosciences, Earth Sciences, Astrophysics and Engineering. Here this method is applied to time series of Acoustic Emissions (AE) signals due to crustal movements, in order to show up possible precursors of catastrophic events. The AE records have been collected, at two different ultrasound frequencies (25 and 150 kHz) and with 30 sec. of sampling rate, in two sites located at Valsinni (Potenza, Italy) and nearby the Peteroa volcano (Argentina). The preliminary results of RQA applied to these AE time series before the earthquake of L'Aquila (Italy, on April 6, 2009), and those concerning the activity of the Andean volcano are shown and seem quite suitable for highlighting incoming paroxysms.