HR: 0800h
AN: G51A-0056    [Abstracts]
TI: One and a Half Year of INSAR Monitoring of Volcanic Activity at Piton de la Fournaise, R\'{e}union Island, With ASAR-ENVISAT Data
AU: Tinard, P
EM: p.tinard@opgc.univ-bpclermont.fr
AF: Laboratoire Magmas et Volcans, Universit\'{e} Blaise Pascal - UMR 6524, 5, rue Kessler, Clermont-Ferrand, 63038 France
AU: Froger, J
EM: jeanluc@cec.uchile.cl
AF: IRD, UR 163 / Laboratoire Magmas et Volcans, Departamento de Geologia, Universidad de Chile, Plaza Ercilla 803, Santiago, 1 Chile
AU: * Fukushima, Y
EM: yofukushima@opgc.univ-bpclermont.fr
AF: Laboratoire Magmas et Volcans, Universit\'{e} Blaise Pascal - UMR 6524, 5, rue Kessler, Clermont-Ferrand, 63038 France
AU: Cayol, V
EM: cayol@opgc.univ-bpclermont.fr
AF: Laboratoire Magmas et Volcans, Universit\'{e} Blaise Pascal - UMR 6524, 5, rue Kessler, Clermont-Ferrand, 63038 France
AU: Briole, P
EM: briole@ipgp.jussieu.fr
AF: CNRS-UMR 7580, Institut de Physique du Globe de Paris, 4, place Jussieu, Paris, 75005 France
AU: Staudacher, T
EM: thomas.staudacher@univ-reunion.fr
AF: Observatoire Volcanologique du Piton de la Fournaise, Institut de Physique du Globe de Paris, 14 RN3, le 27\`{e}me, La Plaine des Cafres, 97418 France
AU: Souriot, T
EM: souriot@opgc.univ-bpclermont.fr
AF: Laboratoire Magmas et Volcans, Universit\'{e} Blaise Pascal - UMR 6524, 5, rue Kessler, Clermont-Ferrand, 63038 France
AB: The activity of Piton de la Fournaise volcano (R\'{e}union Island) was marked by a significant increase during the last one and a half year (April 2003 to September 2004) with eight eruptive episodes. This period coincides with the beginning of systematic data acquisition on Piton de la Fournaise by the radar ASAR on board of the ENVISAT satellite. We have used 80 ASAR images to perform an INSAR monitoring of the Piton de la Fournaise activity. We produced a dataset including more than 150 interferograms which provide an exceptional record of the ground displacements associated with each individual eruption. Thanks to the various angles of view of ASAR, we were able to characterize accurately the EW and vertical components of the displacements. Most of the eruptions exhibit an asymmetric fringe pattern with strong uplift (5 to 15 cm) and horizontal eastward displacement (15 to 45 cm) to the East of the eruptive fissures and with moderate subsidence to the West. These displacements are compatible with the opening of a series of eastward-dipping dikes in the N10$\deg$E and S10$\deg$E trending fracture zones. In contrast, the interferograms spanning the January 2004 eruption show an impressive fringe pattern (40 fringes) extending from the central cone to the Plaine des Osmondes. It could be due either to relatively extended, sill like, magma source or to a decollement. We modeled the displacements associated with the August 2003, September 2003 and May 2004 eruptions using a 3D mixed boundary element method for elastic media. The best-fit models converged towards a set of dikes dipping 45 to 55$\deg$ eastward whose bottoms lie at around 1500 m a.s.l. (depth 800 - 1000 m). The repetitive dike intrusions may have weakened the flank stability by increasing the local strains and then induced the larger displacements of January 2004.
DE: 8419 Eruption monitoring (7280)
DE: 9340 Indian Ocean
DE: 3210 Modeling
DE: 3260 Inverse theory
DE: 1243 Space geodetic surveys
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting