Installation of 5 digital broad-band stations at Volcano island: A contribution to La Fossa seismicity comprehension [Installazione di 5 stazioni digitali a larga-banda sull'isola di Vulcano: un contributo alla conoscenza della sismicità superficiale della Fossa]

arthquakes occurring beneath Vulcano (Aeolian Island, Italy) are associated with fracturing (single events and sporadic, low magnitude swarms) or related to processes of the geothermal system (Montalto, 1994). These latter processes are responsible for most of the background activity, which is represented by weak events originating at shallow depth under the La Fossa cone (H<1.5 Km below sea level). In order to improve the Permanent Seismic Network (PSN) managed by the Istituto Nazionale di Geofisica e Vulcanologia in Catania (INGV-CT) we installed an additional 5 broad-band stations surrounding the La Fossa crater to the 4 already operating there. In particular, in November 2005 along the northern rim of La Fossa cone, 3 digital stations were installed with an array configuration. Thereafter another two stations, were installed at the southern part of the cone base in spring 2007. All the stations are currently in continuous transmission with the INGV Observatory in Lipari. We considered about 1200micro-earthquakes recorded fromJanuary 2004 to July 2007 and likely associatedwith fluid dynamics processes. Studying 1007 of these events, six classes of earthquakes have been recognized by visual inspection, spectral and cross correlation analyses. Three episodes of increasing occurrence accompanying geothermal and geochemical anomalieswere recorded during this time period. The improved seismic network allowed the location of 55 events with unprecedented resolution and to highlight a space distribution depending on the classes of events. The events are mainly located in the central and south-eastern sector of the cone at about 500-1000 metres b.s.l. and events of each class appear to cluster in preferential sectors.