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Observatorio Vulcanologico y Sismologico de Costa Rica, Costa Rica
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- PublicationRestrictedHydrogeology of Stromboli volcano, Aeolian Islands (Italy) from the interpretation of resistivity tomograms, self-potential, soil temperature and soil CO2 concentration measurements(2011)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;Revil, A.; Colorado School of Mines, Department of Geophysics, Golden, CO 80401, USA ;Finizola, A.; Laboratoire GeoSciences Reunion, Universite de la Reunion, Institut de Physique du Globe de Paris, La Reunion, Indian Ocean, France ;Ricci, T.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Delcher, E.; Laboratoire GeoSciences Reunion, Universite de la Reunion, Institut de Physique du Globe de Paris, La Reunion, Indian Ocean, France ;Peltier, A.; Institut de Physique du Globe de Paris, France ;Barde-Cabusson, S.; Institute of Earth Sciences Jaume Almera, Consejo Superior de Investigaciones Cientıficas, Spain ;Avard, G.; Observatorio Vulcanologico y Sismologico de Costa Rica, Costa Rica ;Bailly, T.; Ecole et Observatoire des Sciences de la Terre, Universite de Strasbourg, France ;Bennati, L.; Earth and Atmospheric Sciences Department, Purdue University, West Lafayette, IN, USA ;Byrdina, S.; ISTerre, CNRS, UMR 5559, Universite de Savoie, Equipe Volcan, Le Bourget du Lac, France ;Colonge, J.; Ecole et Observatoire des Sciences de la Terre, Universite de Strasbourg, France ;Di Gangi, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia ;Douillet, G.; Ludwig Maximilians Universitaet, Munich, Germany ;Lupi, M.; University of Bonn, Steinmann Institute, Geodynamics/Geophysics, Germany ;Letort, J.; Ecole et Observatoire des Sciences de la Terre, Universite de Strasbourg, France ;Tsang Hin Sun, E.; Ecole et Observatoire des Sciences de la Terre, Universite de Strasbourg, France; ; ; ; ; ; ; ; ; ; ; ; ; ; ; To 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.481 39 - PublicationRestrictedAdventive hydrothermal circulation on Stromboli volcano (Aeolian Islands, Italy) revealed by geophysical and geochemical approaches: Implications for general fluid flow models on volcanoes(2010)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;Finizola, A.; Laboratoire GéoSciences Réunion, UR, IPGP, UMR 7154, Saint Denis, La Réunion, France ;Ricci, T.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Deiana, R.; Dipartimento di Geoscienze, Università degli Studi di Padova, Padova, Italy ;Barde Cabusson, S.; Dipartimento di Scienze della Terra, Università di Firenze, Firenze, Italy ;Rossi, M.; Dipartimento di Geoscienze, Università degli Studi di Padova, Padova, Italy ;Praticelli, N.; Dipartimento di Geoscienze, Università degli Studi di Padova, Padova, Italy ;Giocoli, A.; Laboratorio di Geofisica, IMAA-CNR, Tito Scalo, Potenza, Italy ;Romano, G.; Tito Scalo, Potenza, Italy ;Delcher, E.; ;Suski, B.; Institut de Géophysique, Université de Lausanne, Lausanne, Switzerland ;Revil, A.; Colorado School of Mines, Illinois St. Golden, Colorado, USA; CNRS-LGIT, UMR 5559, Université de Savoie, Equipe Volcan, Le Bourget du Lac, France ;Menny, P.; Laboratoire Magmas et Volcans, Université Blaise Pascal, Clermont-Ferrand, France ;Di Gangi, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia ;Letort, J.; Ecole et Observatoire des Sciences de la Terre, Université de Strasbourg, France ;Peltier, A.; Institut de Physique du Globe de Paris, UMR 7154, Paris, France ;Villasante-Marcos, V.; Instituto Geografico Nacional, Madrid, Spain ;Douillet, G.; Ecole et Observatoire des Sciences de la Terre, Université de Strasbourg, France ;Avard, G.; Department of Geological Sciences, University of Missouri, USA ;Lelli, M.; Istituto di Geoscienze e Georisorse, CNR, Pisa, Italy; ; ; ; ; ; ; ; ;; ; ; ; ; ; ; ; ; On March 15th 2007 a paroxysmal explosion occurred at the Stromboli volcano. This event generated a large amount of products,mostly lithic blocks, someofwhich impacted the ground as far as down to 200 m a.s.l., about 1.5 kmfaraway fromthe active vents. Two days after the explosion, a newvapouremissionwas discovered on the north-eastern flank of the volcanic edifice, at 560 m a.s.l., just above the area called “Nel Cannestrà”. This new vapour emission was due to a block impact. In order to investigate the block impact area to understand the appearance of the vapour emission, we conducted on May 2008 a multidisciplinary study involving Electrical Resistivity Tomography (ERT), Ground Penetrating Radar (GPR), Self-Potential (SP), CO2 soil diffuse degassing and soil temperature surveys. This complementary data set revealed the presence of an anomalous conductive body, probably related to a shallow hydrothermal level, at about 10–15 m depth, more or less parallel to the topography. It is the first time that such a hydrothermal fluid flow,with a temperature close to thewater boiling point (76 °C) has been evidenced at Stromboli at this low elevation on the flank of the edifice. The ERT results suggest a possible link between (1) the main central hydrothermal system of Stromboli, located just above the plumbing system feeding the active vents, with a maximum of subsurface soil temperature close to 90 °C and limited by the NeoStromboli summit crater boundary and (2) the investigated area of Nel Cannestrà, at ~500 m a.s.l., a buried eruptive fissure active 9 ka ago. In parallel, SP and CO2 soil diffuse degassingmeasurements suggest in this sector at slightly lower elevation fromthe block impact crater a magmatic and hydrothermal fluid rising system along the N41° regional fault. A complementary ERT profile, on May 2009, carried out from the NeoStromboli crater boundary downto the block impact crater displayed a flank fluid flowapparently connected to a deeper system. The concept of shallow hydrothermal level have been compared to similar ERT results recently obtained onMount Etna and La Fossa cone of Vulcano. This information needs to be taken into account in general fluid flow models on volcanoes. In particular, peripheral thermal waters (as those bordering the northeastern coast of Stromboli) could be contaminated by hydrothermal and magmatic fluids coming from regional faults but also from the summit.559 30 - PublicationRestrictedShort-period volcanic gas precursors to phreatic eruptions: Insights from Poás Volcano, Costa Rica(2016)
; ; ; ; ; ; ; ; ; ;; ; ; ;; ;; Volcanic eruptions involving interaction with water are amongst the most violent and unpredictable geologic phenomena on Earth. Phreatic eruptions are exceptionally difficult to forecast by traditional geophysical techniques. Here we report on short-term precursory variations in gas emissions related to phreatic blasts at Poás volcano, Costa Rica, as measured with an in situ multiple gas analyzer that was deployed at the edge of the erupting lake. Gas emitted from this hyper-acid crater lake approaches magmatic values of SO2/CO2 1–6 days prior to eruption. The SO2 flux derived from magmatic degassing through the lake is measureable by differential optical absorption spectrometry (sporadic campaign measurements), which allows us to constrain lake gas output and input for the major gas species during eruptive and non-eruptive periods. We can further calculate power supply to the hydrothermal system using volatile mass balance and thermodynamics, which indicates that the magmatic heat flux into the shallow hydrothermal system increases from ∼27 MW during quiescence to ∼59 MW during periods of phreatic events. These transient pulses of gas and heat from the deeper magmatic system generate both phreatic eruptions and the observed short-term changes in gas composition, because at high gas flux scrubbing of sulfur by the hydrothermal system is both kinetically and thermodynamically inhibited whereas CO2 gas is always essentially inert in hyperacid conditions. Thus, the SO2/CO2 of lake emissions approaches magmatic values as gas and power supply to the sub-limnic hydrothermal system increase, vaporizing fluids and priming the hydrothermal system for eruption. Our results suggest that highfrequency real-time gas monitoring could provide useful short-term eruptive precursors at volcanoes prone to phreatic explosions172 6 - PublicationOpen AccessA New Sulfur and Carbon Degassing Inventory for the Southern Central American Volcanic Arc: The Importance of Accurate Time-Series Data Sets and Possible Tectonic Processes Responsible for Temporal Variations in Arc-Scale Volatile Emissions(2017-12-12)
; ; ; ; ; ; ; ; ; ; ; ; ; ;; ; ; ; ;This work presents a new database of SO2 and CO2 fluxes from the Southern Central American Volcanic Arc (SCAVA) for the period 2015–2016. We report 300 SO2 flux measurements from 10 volcanoes and gas ratios from 11 volcanoes in Costa Rica and Nicaragua representing the most extensive available assessment of this 500 km arc segment. The SO2 flux from SCAVA is estimated at 6,24061,150 T/d, about a factor of three higher than previous estimations (1972–2013). We attribute this increase in part to our more complete assessment of the arc. Another consideration in interpreting the difference is the context of increased volcanic activity, as there were more eruptions in 2015–2016 than in any period since 1980. A potential explanation for increased degassing and volcanic activity is a change in crustal stress regime (from compression to extension, opening volcanic conduits) following two large (Mw>7) earthquakes in the region in 2012. The CO2 flux from the arc is estimated at 22,50064,900 T/d, which is equal to or greater than estimates of C input into the SCAVA subduction zone. Time-series data sets for arc degassing need to be improved in temporal and spatial coverage to robustly constrain volatile budgets and tectonic controls. Arc volatile budgets are strongly influenced by short-lived degassing events and arc systems likely display significant short-term variations in volatile output, calling for expansion of nascent geochemical monitoring networks to achieve spatial and temporal coverage similar to traditional geophysical networks.86 29 - PublicationOpen AccessTurmoil at Turrialba Volcano (Costa Rica): Degassing and eruptive processes inferred from high-frequency gas monitoring(2016-08)
; ; ; ; ; ; ; ; ; ; ; ; ;; ; ; ; ; ;; ; ; ;Eruptive activity at Turrialba Volcano (Costa Rica) has escalated significantly since 2014, causing airport and school closures in the capital city of San José. Whether or not new magma is involved in the current unrest seems probable but remains a matter of debate as ash deposits are dominated by hydrothermal material. Here we use high-frequency gas monitoring to track the behavior of the volcano between 2014 and 2015 and to decipher magmatic versus hydrothermal contributions to the eruptions. Pulses of deeply derived CO2-rich gas (CO2/Stotal > 4.5) precede explosive activity, providing a clear precursor to eruptive periods that occurs up to 2 weeks before eruptions, which are accompanied by shallowly derived sulfur-rich magmatic gas emissions. Degassing modeling suggests that the deep magmatic reservoir is ~8-10 km deep, whereas the shallow magmatic gas source is at ~3-5 km. Two cycles of degassing and eruption are observed, each attributed to pulses of magma ascending through the deep reservoir to shallow crustal levels. The magmatic degassing signals were overprinted by a fluid contribution from the shallow hydrothermal system, modifying the gas compositions, contributing volatiles to the emissions, and reflecting complex processes of scrubbing, displacement, and volatilization. H2S/SO2varies over 2 orders of magnitude through the monitoring period and demonstrates that the first eruptive episode involved hydrothermal gases, whereas the second did not. Massive degassing (>3000 T/d SO2and H2S/SO2 > 1) followed, suggesting boiling off of the hydrothermal system. The gas emissions show a remarkable shift to purely magmatic composition (H2S/SO2 < 0.05) during the second eruptive period, reflecting the depletion of the hydrothermal system or the establishment of high-temperature conduits bypassing remnant hydrothermal reservoirs, and the transition from phreatic to phreatomagmatic eruptive activity.189 46