Ricerc@Sapienza

Deformation signals recorded at volcanoes have long been used to investigate volcanic processing. Parameters such as location, depth, and volume change can be inferred from the ground displacements measured on the Earth¿s surface by applying inversion techniques. Deformation measurements at active volcanoes are usually made with continuous Global Positioning System (CGPS) stations, supplemented by Interferometric Synthetic Aperture Radar (InSAR) images. InSAR can image ground deformation over large areas at centimeter-scale resolution over time-scales of days to a few years, while CGPS can provide continuous information on three-dimensional ground displacements at a network of key sites. Nevado del Ruiz volcano rises 5321 meters above sea level in the Colombian Andes. In November 1985, pyroclastic material fall from a modest explosive eruption led to the sudden melting of the volcano ice-cap, and the formation of a lahar that reached and destroyed the town of Armero and part of the town of Chinchina causing 25000 dead. After a decade of quiescence, in 2010 Nevado del Ruiz entered in the present period of unrest with a significant increase in seismicity, surface deformation and gas venting. We will investigate the interaction between the volcano magmatic system and local tectonics to explain the present volcanic unrest. Analysis of GPS displacements from 2010 to present, and InSAR from 2012 to 2015, will allow to constrain the source of unrest and infer the local stress transfer controlling the subsurface magma and fluid flow. The analysis will be based on both analytical and numerical inversion of geodetic data. We will first employ analytical models to constrain the source of unrest. Then we will develop numerical Finite Element Method models to evaluate the influence of irregular geometries, volcanic topography, heterogeneous material properties and various rheologies on the local stress transfer and the evolution of the volcanic unrest.