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Galeras volcano conduit dynamics revealed by ALOS-2/PALSAR interferometry (2015-2023)

Sindy Lizarazo1, Fabien Albino2, Valerie Cayol1

  • Affiliations: 1 Équipe de Volcanologie, Laboratoire Magmas et Volcans (LMV) - Université Clermont-Auvergne, Clermont-Ferrand, France 2 Équipe de Géophysique des volcans et Géothermie, Institut des Sciences de la Terre (ISTerre) - Université Grenoble-Alpes, Grenoble, France

  • Presentation type: Poster

  • Presentation time: Friday 16:30 - 18:00, Room Poster Hall

  • Poster Board Number: 33

  • Programme No: 2.3.19

  • Theme 2 > Session 3

Abstract

The detection of precursory deformation signals presents several challenges at tropical stratovolcanoes. These challenges are related to dense vegetation, strong topography gradient, and rapidly changing atmospheric conditions that introduce noise in observations derived from ground instrumentation and satellite imagery. Moreover, the spatial resolution of GNSS networks is limited for a continuous mapping of surface displacements, and subsequent precise modeling of internal sources. These limitations were addressed by analyzing ALOS-2/PALSAR images at Galeras volcano characterized for being one of the most active ones in Colombia. Tropospheric noise correction methods were  based on external datasets such as weather models and local GNSS data, and on the removal of correlated signals between elevation and deformation. Their performance at reducing noise on the interferometric phase was assessed statistically. As a result, precise cumulative displacement maps and time series were obtained for the period 2014-2023. A persistent subsiding circular signal with a radius of ~0.25 km is retrieved at the volcano's summit from ascending and descending geometries. Using the Boundary Element Method (BEM) software DefVolc, we model cumulative ground displacements on the order of ~0.08 m by a vertically elongated ellipsoidal source located at ~0.60 km depth below the main crater. Integrating additional datasets, such as seismological tomography and gas measurements, can refine the interpretation of the causes behind the volcano's conduit volume change and provide deeper insights into the current state of the magmatic system.