GNGTS 2022 - Atti del 40° Convegno Nazionale

GNGTS 2022 Sessione 1.2 95 STA/LTA AUTOMATIC CUT OF EXPLOSION QUAKES A. Di Benedetto 1 , A. Figlioli 2 , A. D’Alessandro 3 , G. Lo Bosco 1 1 Dipartimento di Matematica e Informatica, Università degli studi di Palermo, Palermo, Italy 2 Dipartimento di Scienze della Terra e del Mare, Università degli studi di Palermo, Palermo, Italy 3 Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Nazionale Terremoti, Rome, Italy Introduction. The scientific community is committed to identifying and analysing seismic signals produced by volcanic activity, with the aim of characterizing possible precursors in order to using them as a pre-warning of activity. The most dangerous activity which has a greater impact on the population living in the inhabited centres adjacent to the volcano is paroxysm (Giudicedipietro et al. , 2020). In particular, one of the most dangerous volcano is Stromboli. Stromboli volcano (926 m l.s.m.) belongs to the Aeolian archipelago in the Mediterranean Sea (Italy); it is geodinamically located between the subduction Ionian slab and the Tyrrhenian Sea. It is an open conduit, characterized by three summit craters (Fig. 1), with persistent strombolian activity, whose explosions occur every 15-20 minutes. Generally, its volcanic activity is classified into three classes: normal activity (precisely “explosion”), major explosion and paroxysm. To distinguish them, the variation of frequency and energy of activity has to be calculated (Calvari et al. , 2021). The permanent seismic network of INGV (Istituto Nazionale di Vulcanologia e Geofisica) is able to record seismic signals corresponding to the volcanic explosions, which are differentiated by: VLP (very long period), landslides, tornillos, Explosion Quakes (EQ). The main focus of this work is on this latter class, because clearly visible by the human eye along a seismic path. Their features are based on the variation in amplitude and frequency content, whose range is around 10-25 Hz. Another characteristic is that the EQ is preceded by VLP, and it is important in order to identify itself (Giudicepietro et al. , 2019). This feature allows describing the phenomena that occur in the plumbing system. In detail, the mechanism that activates the VLP and successively EQ, is a progressive degassing magma on the conduit. When the intensive increases, the conduit goes into resonance with the wall and produces a seismic wave. After the magma starts the migration and then arrives in the vent, the strombolian activity starts and in the raw signal, one can observe the EQ. The Stromboli systems are characterized by two reservoirs: a shallow conduit located by 3-4 km and a deep reservoir located by 11 km (Harris and Ripepe, 2007). Fig. 1 - INGV seismic network on Stromboli.