Hydrogeology of Stromboli volcano, Aeolian Islands (Italy) from the interpretation of resistivity tomograms, self-potential, soil temperature and soil CO2 concentration measurements

Abstract

International audienceTo gain a better insight of the hydrogeology and the location of the main tectonic faults of Stromboli volcano in Italy, we collected electrical resistivity measurements, soil CO2 concentrations, temperature and self-potential measurements along two profiles. These two profiles started at the village of Ginostra in the southwest part of the island. The first profile (4.8 km in length) ended up at the village of Scari in the north east part of the volcano and the second one (3.5 km in length) at Forgia Vecchia beach, in the eastern part of the island. These data were used to provide insights regarding the position of shallow aquifers and the extension of the hydrothermal system. This large-scale study is complemented by two high-resolution studies, one at the Pizzo area (near the active vents) and one at Rina Grande where flank collapse areas can be observed. The Pizzo corresponds to one of the main degassing structure of the hydrothermal system. The main degassing area is localized along a higher permeability area corresponding to the head of the gliding plane of the Rina Grande sector collapse. We found that the self-potential data reveal the position of an aquifer above the villages of Scari and San Vincenzo. We provide an estimate of the depth of this aquifer from these data. The lateral extension of the hydrothermal system (resistivity ∼15-60 ohm m) is broader than anticipated extending in the direction of the villages of Scari and San Vincenzo (in agreement with temperature data recorded in shallow wells). The lateral extension of the hydrothermal system reaches the lower third of the Rina Grande sector collapse area in the eastern part of the island. The hydrothermal body in this area is blocked by an old collapse boundary. This position of the hydrothermal body is consistent with low values of the magnetization (<2.5 A m−1) from previously published work. The presence of the hydrothermal body below Rina Grande raises questions about the mechanical stability of this flank of the edifice

Investigating the deepest part of a volcano plumbing system: Evidence for an active magma path below the western flank of Piton de la Fournaise (La Réunion Island)

“…Many recent studies used soil CO 2 diffuse emissions as a useful and unambiguous tracer of volcanic and tectonic structures ( Azzaro et al, 1998;Giammanco et al, 1998;Finizola et al, 2003Finizola et al, , 2004Revil et al, 2008Revil et al, , 2011Bennati et al , 2011;Bonforte et al, 2013). In this study of the NWRZ of Piton de la Fournaise, we adopted a multidisciplinary approach combining (1) soil CO 2 flux and isotopic data, (2) seismic events spanning from 1996 to 2015, (3) a photogrammetric model to quantify the dyke distribution and orientation and, finally, (4) the spatial density of the cinder cones in the area investigated, with the aim of identifying and better constraining potentially active structures within this rift zone.…”

Architecture and temporal variations of a terrestrial CO2 degassing site using electric resistivity tomography and self-potential

“…While many studies have focused on CO 2 capture and storage sites, far fewer studies exist that used geoelectrical methods at natural, terrestrial degassing sites. Most of these CO 2 degassing studies either used geoelectrical methods (Flechsig et al 2008;Nickschick et al 2015;Pettinelli et al 2010;Schütze et al 2012a, b) or combined them with self-potential methods (Revil et al 2008(Revil et al , 2011Byrdina et al 2009;Finizola et al 2010;Sandig et al 2014;Sauer et al 2013). Although all of these studies can reveal the underground structure of degassing sites (Ramirez et al 2003;Bergmann et al 2012Bergmann et al , 2016, the aspect of changes over time within these degassing sites has only been scarcely researched (Drahor et al 2012;Fedele et al 2015).…”

Radon mapping, automatic measurements and extremely high 222Rn emissions during the 2002–2007 eruptive scenarios at Stromboli volcano

“…The hydrothermal system of Stromboli volcano is essentially concentrated in the surrounding of the summit area (Finizola et al, 2002;. However, the presence of thermal waters and vapors in the surrounding of the Stromboli village together with radon anomalies and low resistivity layers suggests the extension of the hydrothermal shell at lower altitudes (Carapezza et al, 2004;Cigolini et al, 2005;Revil et al, 2011).…”