HR: 11:35h
AN: GP32A-06    [Abstracts]
TI: The 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 soil CO2 gas measurements
AU: Revil, A
EM: arevil@mines.edu
AF: Colorado School of Mines, Green's center, 1500 Illinois street, Golden, 80401, United States
AU: * Finizola, A
EM: anthony.finizola@univ-reunion.fr
AF: Laboratoire GéoSciences Laboratoire GéoSciences Laboratoire Géoscience Réunion, UMR CNRS-IPGP 7154, Université de La Réunion, 15, rue René Cassin La Réunion (France), Saint Denis cedex 9, 97715, France
AB: La Fossa cone is an active stratovolcano located on Vulcano Island, in the Aeolian Archipelago (southern Italy). Its activity is characterized by explosive phreatic eruptions and phreato-magmatic eruptions producing wet and dry pyroclastic surges, pumice fall deposits and highly viscous lava flows. Nine profiles of 2D high resolution Electrical Resistivity Tomography (ERT) (electrode spacing 20 meters, with a depth of penetration > 200 meters) were performed across this edifice to image its inner structure. In addition, we also measured the self-potential, the flux of CO2, and the temperature along these profiles. These data provide complementary information to interpret the ERT profiles. The ERT profiles allow to identify the main structural boundaries (and their associated fluid circulations) structuring the shallow architecture of the Fossa cone. The hydrothermal system is identified by very low values of the electrical resistivity (< 20 Ù m). Its lateral extension is clearly limited by the crater boundaries, which are relatively resistive (> 400 Ù m). Inside the crater, it is possible to follow the plumbing system of the main fumarolic area at depth. On the flank of the edifice, a thick layer of tuff is also marked by low resistivity values (in the range 1 to 20 Ù m). The ashes and pyroclastic materials ejected during the XIX Century eruptions and covering the flank of the volcano corresponds to relatively resistive materials (several hundreds to several thousands Ù m). Laboratory measurements are performed to determine the streaming coupling coefficient of the main materials forming the edifice. A 2D simulation of the ground water flow is performed over the edifice using the finite element code Comsol Multiphysics 3.3. Forward and inverse modeling of the self- potential data can be used to put constraints on the flux of water in the flanks of the edifice and inside the crater. The result reveals the very high potentiality of these methods for high resolution imaging of the inner structure of an active volcano.
UR: http://www.andre-revil.com/
DE: 0903 Computational methods: potential fields (1214)
DE: 0925 Magnetic and electrical methods (5109)
DE: 0933 Remote sensing
DE: 5109 Magnetic and electrical properties (0925)
DE: 5139 Transport properties
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Fall Meeting