Ground deformation at the Cerro Blanco caldera: A case of subsidence at the Central Andes BackArc

• Published in: Journal of South American earth sciences 2021-03, Vol.106 (C), p.102941, Article 102941
• Main Authors: Vélez, M.L, Bustos, E., Euillades, L., Blanco, M., López, J.F.S., Barbero, I., Berrocoso, M., Gil Martinez, A., Viramonte, J.G.
• Format: Article
• Language: English
• Subjects: COSMO-SkyMed; DInSAR; Envisat; GPS; Sentinel-1; Southern Puna; Volcanic deformation
• ISSN: 0895-9811; 1873-0647
• DOI: 10.1016/j.jsames.2020.102941

Cerro Blanco Volcanic Complex (CBVC) is one of the youngest caldera complexes in the Southern Central Andes. Subsidence registered at CBVC has shown a slowdown in deformation velocity since 1992 (2.6 cm/yr) to 2010 (0.87 cm/yr). We update the deformation state of this caldera system by processing DInSAR data between 2003 and 2020 and GPS as a complementary tool. Results showed a circular deformation pattern of about 12 km diameter related to subsidence centered at CBVC throughout the entire period under analysis. Deformation rate decreased from 1 cm/yr for 2003–2009 period (Envisat data) to 0.7 cm for the 2012–2020 period (COSMO-SkyMed and Sentinel-1 data). Rate values were confirmed with GPS measurements during 2004 and 2013–2015. Analytical inverse modelling was used to infer the main characteristic of the source responsible for the measured displacement. Best-fitting solution corresponded to a spherical source located between 9 and 14 km from the surface with a volume decrease of about −0.013 km3/yr for the entire period. We propose that a combination of magmatic and geothermal dynamic as the origin of the continuous and slow subsidence observed in the CBVC as a consequence of the last eruption that occurred ca. 4 ka ago. •DInSAR processing and GPS were used to measure the deformation in CBVC.•Continuous and slow subsidence is observed in CBVC from 2003 to 2020.•Subsidence is caused mainly by the cooling and solidification of a mid-crust magmatic body.•Outgassing from the geothermal reservoir would be also contributing to the observed subsidence.