Possible structural control on the 2011 eruption of Puyehue-Cordón Caulle Volcanic Complex (southern Chile) determined by InSAR, GPS and seismicity

Abstract

The Puyehue-Cordon Caulle Volcanic Complex (PCCVC) is one of the best examples of tectonic control on volcanism at the Southern Volcanic Zone of the Andes (southern Chile). The PCCVC comprises several volcanic centres that erupted dominantly SiO2-rich magmas at the intersection of the trench-parallel Liquine-Ofqui Fault Zone (LOFZ) and an inherited NW-SE basement structure. The PCCVC began an explosive and later effusive eruption on 2011 June 4 causing decimetre-to metre-scale surface deformation that was observed by a series of Envisat ASAR satellite scenes. We modelled this data and complemented it with timeseries of two continuous GPS stations and seismicity recorded by a local network. Deformation during the first 3 days of the eruption can be modelled either by two point sources aligned with the NW-SE Cordon Caulle graben or by a closing dyke with a significant component of left-lateral motion along the graben. These models are discussed with respect to their implications on the estimated rheology and the eruption mechanism. GPS observations near the volcanic complex reveal an additional, more localised effect related to the LOFZ in the south of the complex. Coeruptive deformation at the main geological structures of the PCCVC is further supported by relocated seismicity, which is concentrated along the Cordon Caulle graben and to the western side of the LOFZ.