Opportunities of satellite based remote sensing for the long-term monitoring of volcanoes

Abstract

Volcanoes cause significant risk on local, regional and global scales during their eruptive phases owing to lava and pyroclastic flows, ash and tephra fallout, landslides, lahars and volcanic gas discharge. This work addresses the opportunities of satellite based remote sensing for the long-term monitoring of volcanoes. Primary goals are to create an understanding and an overview of the technical potential of the monitoring of volcanoes regarding various detection objectives and the use of various techniques in Peru, Chile and Ecuador for both the Andean region and the Galápagos archipelago. This analysis has the ulterior motive of creating a base for a natural hazard early warning system in the Andes. A share of 26 volcanoes in Peru, Chile and Ecuador showing eruptive activity since 1980, that was detected by satellites, are analyzed in detail. Mainly secondary literature is examined for described detection results – the information put in order according to used techniques and satellites or sensors, as well as resolution and detection objectives. Additionally a morphological analysis is performed consisting of 3D Google Earth models, W-E profiles of the volcanoes and a comparison to TerraSAR-X or Sentinel-1 images to find areas on the edifices affected by distortions. Volcanoes can be monitored in a pre-, co- and post-eruptive phase of the eruption cycle. Precursors of eruptions can be detected by SAR deformation and thermal analysis which demands frequent analysis. Additionally deformation detection requires a high actuality of the SAR image taken before the eruption to create successful interferograms. Important is also the observation that deformations may start to occur months before the actual event while thermal precursors become visible shortly before the eruption. The detection of some precursor activities such as fumarolic activity requires medium resolution as provided by ASTER images. Co- and post-eruptive SAR surface roughness and optical change analysis becomes available, but due to their lack of pre-eruptive monitoring opportunities the frequency of analysis may be reduced to major eruption occurrence only. Both have great potential for snow and glacier topped volcanoes. The resolution of open access data of e.g. Sentinel-1, ASTER, MODIS and Landsat are sufficient for basic analysis. The data acquisition is exemplary performed with the volcanoes Fernandina, Reventador, Sabancaya, Villarrica. The effusive fissure eruption of the Bardarbunga volcano in Iceland in 2014 and 2015 functions as a positive example of an extensive pre-eruptive monitoring and co-/ posteruptive reprocessing. Satellite images were collected and the projected lava flow extent digitalized. The lava flow extent development over time between August 2014 and March 2015 is shown in an map and in a diagram in comparison to reference data obtained from reports by the University of Iceland.