IDEAN   23403
INSTITUTO DE ESTUDIOS ANDINOS "DON PABLO GROEBER"
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
1. Deflation of Copahue Volcanic System, Deformation Source Models from Inversion of Satellite Radar Interferometry Data Using a Genetic Algorithm.
Autor/es:
2. VELEZ MARÍA LAURA (1), EUILLADES PABLO (2), CASELLI ALBERTO TOMÁS (1), BLANCO MAURO (2)
Lugar:
Tenerife, Islas Canarias
Reunión:
Congreso; Cities on Volcanoes 6; 2010
Institución organizadora:
IAVCEI
Resumen:
1.       Copahue volcano (37° 45.35’S, 71° 11’ W, 2997 m.a.s.l) is one of the most active volcanoes in Argentina. It is an active andesitic to basaltic-andesitic stratovolcano, nested on the western rim of the Caviahue caldera, straddling the border between Argentina and Chile. The volcano summit has nine craters aligned in N60°E direction; the easternmost crater is presently active, and its filled with an acid-water lake of about 200 m in diameter. Historical eruptions have been reported on 1992, 1995 and 2000. The last eruptive cycle involved ash and gas emissions and it is considered to be Copahue´s most vigorous activity in the past century. We have performed an interferometric analysis of Synthetic Aperture Radar images (InSAR) of the area, using a total data set of 18 ascending ENVISAT ASAR radar images (IS2, polarization-VV) from December-2002 to November-2007, 43 differential interferograms were constructed and combined by using Small Baseline Subsets algorithm. A mean velocity of 1.8 cm/yr was calculated, assuming the deformation rate constant during the time period of the interferograms. The deflation is mostly located on the northeastern flank of the volcano. We evaluate the geometry of the magma chamber from inversion of interferometric data. The signal was modelled assuming a uniform elastic isotropic half-space with Poisson´s ratio 0.25 and rigidity modulus of 30-GPa. We used an inversion procedure employing a genetic algorithm to identify best fit source parameters. We tested two models, a point pressure source, known as Mogi source (Mogi, 1958), and an ellipsoidal source (Yang et al., 1988). Model results indicate a deformation source located at a mean depth of 4 Km, with a mean volume change of 0.0015 Km3/yr, interpreted as decompression due to a perturbation of the magmatic-hydrothermal system. References: Mogi, K. 1958 BERI 36, 99-134. Yang, X.M., Davis, P.M., Dieterich, J.H., 1988. JGR, 93, 4249-4257.