Investigating Hydrothermal and Magmatic Deformation using Geodetic Time Series at Uturuncu Volcano, Bolivia

Abstract:

In order to identify the subsurface processes behind several decades of surface elevation change at one of the world’s most extensive mid-crustal magma bodies, we analyze new Interferometric Synthetic Aperture Radar (InSAR) observations through 2020. Uturuncu Volcano is located in the southern Bolivian Andes, above the Altiplano-Puna Magma Body, and has not erupted in about 250 ka. Satellite InSAR data spanning 1992-2010 captured a region of uplift surrounded by a moat of subsidence 150 km in diameter centered on Uturuncu. More recent work has shown continued deformation through 2017 with uplift rates that have slowed to <1 cm/yr and an area of localized subsidence to the south-southwest of Uturuncu. Deformation at the volcano edifice, the area of local subsidence, and the long wavelength subsidence are of particular interest because of what they can tell us about both shallow and deep sources of deformation. Previous work explores a range of models including an ascending diapir, mush reorganization, hydrothermal activity, and brine lens dynamics to explain the deformation patterns. The time scales of the deformation events can test the likelihood of these models. A constant, long-term uplift could support a rising diapir and spatially variable regions of short-term uplift or subsidence could support shallow hydrothermal activity. We use ISCE2 software to create interferograms that span from Nov. 2014 to present from two ascending and two descending tracks of Sentinel-1 data and produce time series of surface elevation change in the satellite’s line of sight (LOS). We combine the Sentinel-1 data with GNSS, TSX and Envisat data to investigate multiple sources of deformation at Uturuncu. Based on our analysis of the Sentinel-1 measurements, the edifice is uplifting at about 1-2 mm/yr from 2014 to 2020. The local subsidence approximately 11 km south-southwest of the edifice appears to have stopped, going from LOS velocities of 3-4 mm/yr from 2014 to early 2017 to rates below the noise threshold from 2017 to present. The different temporal and spatial scales of these signals indicate a complex system displaying activity at multiple depths.