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

M. L. VÉLEZ; E. BUSTOS; L. EUILLADES; M. BLANCO; J. F. S. LÓPEZ; I. BARBERO; M. BERROCOSO; A. GIL MARTINEZ; J. G. VIRAMONTE

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2021 vol. 106

0895-9811

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.