GNGTS 2017 - 36° Convegno Nazionale

GNGTS 2017 S essione 1.3 203 The eruption of 13 November 1985 caused a major disaster in Colombia because the ash fall from a modest explosion in the Arenas crater led to the sudden melting of the volcano ice-cap and the formation of a lahar that reached and destroyed the town Armero and some neighborhoods of the town of Chinchina, causing 25,000 dead. Due to its past eruption history, studying this volcanic complex using ground deformation data has a considerable value for understanding the physical processes controlling its behavior. Furthermore, there is a real need to use this information to serve the communities around the volcano and reduce the volcanic risk. The volcano has an efficient seismological, geodetic and geochemical monitoring network run by the Colombian Geological Survey by the Volcanological and Seismological Observatory of Manizales. The deformation of Nevado del Ruiz has been monitored since 1985 and in the last years the geodetic network has been enhanced with electronic tiltmeters (since 2007) and permanent GPS stations (since 2011) (Ordoñez et al. , 2015). To the present day the GPS monitoring network of Nevado del Ruiz Volcano is defined by eight stations (BIS, BLLR, GUAL, NERE, OLLE, RUBI, PIRA and SINN) located around the Volcano (Fig. 1). The monitoring record shows that Nevado del Ruiz has been continuously active since 2010 (Fig. 2). This activity includes an increase in seismicity, large gases and ash emissions, deformation and moderate explosive eruptions (VEI = 2) such as those in May and June 2012. Gps Monitoring network and data processing. GPS is a system of military origin, used since the second half of the eighties also for the study of the Earth’s shape (Geodesy). The three-dimensional nature of GPS measurements allows to record vertical as well as horizontal displacements at benchmarks of a monitoring network with extremely high accuracy (error less than 1 cm). The receivers installed at the permanent GPS sites (CGPS) monitoring Nevado del Ruiz are Trimble Model NetR9, configured to be operated as a continuous operation reference station (CORS) with recording and data storage every 30 seconds and daily file generation. The receivers can acquire satellite signals from the GPS system (L1, L2, L2C and L5) and the GLONAS system (L1 / L2). Additionally, They can acquire signals based on the SBAS (Space Based Augmentation System) technology of both American WAAS signals, as well as EGNOS Fig. 2 - Comparison between seismicity (volcano-tectonic, long period and hybrid events), deformation (GPS and tilt data), and gas (SO2) flux.