Inner structure of La Fossa di Vulcano (Vulcano Island, southern Tyrrhenian Sea, Italy) revealed by high-resolution electric resistivity tomography coupled with self-potential, temperature, and CO2 diffuse degassing measurements

A. Revil; Anthony Finizola; A. Piscitelli; E. Rizzo; T. Ricci; A. Crespy; B. Angeletti; M. Balasco; Stéphanie Barde-Cabusson; L. Bennati; A. Boleve; S. Byrdina; N. Carzaniga; F. Di Gangi; Julie Morin; A. Perrone; M. Rossi; E. Roulleau; B. Suski

doi:10.1029/2007JB005394

Inner structure of La Fossa di Vulcano (Vulcano Island, southern Tyrrhenian Sea, Italy) revealed by high-resolution electric resistivity tomography coupled with self-potential, temperature, and CO2 diffuse degassing measurements

A. Revil ^{1, 2, 3} Anthony Finizola ^{4, 5, 6} A. Piscitelli ⁷ E. Rizzo ⁷ T. Ricci ⁴ A. Crespy ² B. Angeletti ² M. Balasco ⁷ Stéphanie Barde-Cabusson ⁸ L. Bennati ^{8, 9} A. Boleve ^{1, 10} S. Byrdina ^{5, 8} N. Carzaniga ¹¹ F. Di Gangi ⁴ Julie Morin ⁶ A. Perrone ⁷ M. Rossi ⁵ E. Roulleau ¹² B. Suski ¹³

1 LGIT - Laboratoire de Géophysique Interne et Tectonophysique

2 Université Paul Cézanne - Aix-Marseille 3

3 Colorado school of Mines

4 INGV - Istituto Nazionale di Geofisica e Vulcanologia

5 IPGP - Institut de Physique du Globe de Paris

6 LGSR - Laboratoire GéoSciences Réunion

7 Laboratory of Geophysics

8 LMV - Laboratoire Magmas et Volcans

9 Department of Earth and Atmospheric Sciences

10 SOBESOL

11 Department of Geology and Geosciences

12 GEOTOP Centre de recherche en géochimie et géodynamique

13 Institut de Geophysique

Abstract : La Fossa cone is an active stratovolcano located on Vulcano Island in the Aeolian Archipelago (southern Italy). Its activity is characterized by explosive phreatic and phreatomagmatic eruptions producing wet and dry pyroclastic surges, pumice fall deposits, and highly viscous lava flows. Nine 2-D electrical resistivity tomograms (ERTs; electrode spacing 20 m, with a depth of investigation >200 m) were obtained to image the edifice. In addition, we also measured the self-potential, the CO2 flux from the soil, and the temperature along these profiles at the same locations. These data provide complementary information to interpret the ERT profiles. The ERT profiles allow us to identify the main structural boundaries (and their associated fluid circulations) defining the shallow architecture of the Fossa cone. The hydrothermal system is identified by very low values of the electrical resistivity (<20 Ω m). Its lateral extension is clearly limited by the crater boundaries, which are relatively resistive (>400 Ω m). Inside the crater it is possible to follow the plumbing system of the main fumarolic areas. On the flank of the edifice a thick layer of tuff is also marked by very low resistivity values (in the range 1–20 Ω m) because of its composition in clays and zeolites. The ashes and pyroclastic materials ejected during the nineteenth-century eruptions and partially covering the flank of the volcano correspond to relatively resistive materials (several hundreds to several thousands Ω m). We carried out laboratory measurements of the electrical resistivity and the streaming potential coupling coefficient of the main materials forming the volcanic edifice. A 2-D simulation of the groundwater flow is performed over the edifice using a commercial finite element code. Input parameters are the topography, the ERT cross section, and the value of the measured streaming current coupling coefficient. From this simulation we computed the self-potential field, and we found good agreement with the measured self-potential data by adjusting the boundary conditions for the flux of water. Inverse modeling shows that self-potential data can be used to determine the pattern of groundwater flow and potentially to assess water budget at the scale of the volcanic edifice.

Keywords : hydrothermal system soil CO2 degassing self-potential electrical resistivity

Type de document :

Article dans une revue

Journal of Geophysical Research : Solid Earth, American Geophysical Union, 2008, 113 (B7), pp.B07207. 〈10.1029/2007JB005394〉

Domaine :

Planète et Univers [physics] / Sciences de la Terre / Volcanologie

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Dernière modification le : jeudi 11 octobre 2018 - 01:17:15

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Inner structure of La Fossa di Vulcano (Vulcano Island, southern Tyrrhenian Sea, Italy) revealed by high-resolution electric resistivity tomography coupled with self-potential, temperature, and CO2 diffuse degassing measurements

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Inner structure of La Fossa di Vulcano (Vulcano Island, southern Tyrrhenian Sea, Italy) revealed by high-resolution electric resistivity tomography coupled with self-potential, temperature, and CO2 diffuse degassing measurements

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