Deformation of Copahue volcano: inversion of InSAR data using a genetic algorithm

MARIA LAURA VELEZ; PABLO EUILLADES; ALBERTO CASELLI; MAURO BLANCO; JOSÉ MARTÍNEZ DÍAZ

JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2011 vol. 202 p. 117 - 126

0377-0273

The Copahue volcano is one of the most active volcanoes in Argentina with eruptions having been reported asrecently as 1992, 1995 and 2000. A deformation analysis using the Differential Synthetic Aperture Radartechnique (DInSAR) was performed on Copahue?Caviahue Volcanic Complex (CCVC) from Envisat radarimages between 2002 and 2007. A deformation rate of approximately 2 cm/yr was calculated, located mostlyon the north-eastern flank of Copahue volcano, and assumed to be constant during the period of theinterferograms. The geometry of the source responsible for the deformation was evaluated from an inversionof the mean velocity deformation measurements using two different models based on pressure sourcesembedded in an elastic homogeneous half-space. A genetic algorithm was applied as an optimization tool tofind the best fit source. Results from inverse modelling indicate that a source located beneath the volcanoedifice at a mean depth of 4 kmis producing a volume change of approximately 0.0015 km/yr. This source wasanalysed considering the available studies of the area, and a conceptual model of the volcanic?hydrothermalsystem was designed. The source of deformation is related to a depressurisation of the system that resultsfrom the release of magmatic fluids across the boundary between the brittle and plastic domains. Theseleakages are considered to be responsible for the weak phreatic eruptions recently registered at the Copahuevolcano