Surface deformation of the Eastern Central Andes, observed by wide-swath radar interferometric time-series.

Active deformation in the Eastern Central Andes backarc involves ongoing east-west shortening, and crustal strain with the potential to trigger a Mw 7.8 earthquake is accumulating, as indicated by geological records and geodetic data. We focus on the sparsely instrumented northwestern Argentina and southwestern Bolivia to quantify and localize ongoing E–W shortening of the Eastern Andes, and to characterize localized deformation related to other active processes in the backarc. 

We analyzed ten years of Interferometric Synthetic Aperture Radar (InSAR) data to measure rates of surface deformation and generate time series. We rely on descending ALOS-2 radar imagery (L-band) and wide-swath (~350 km) ScanSAR mode. We used the “alos2stack” workflow in the ISCE-2 software, and substantially downsampled the interferograms to suppress noise, resulting in a ground-range pixel spacing of ~136 m. We then generated deformation time-series with the MintPy software and applied corrections for topography, solid Earth tides, and stratified tropospheric signal delay using ERA5 weather models. We further applied a range split-spectrum method to suppress the ionospheric phase contribution.  

The resulting surface deformation rate maps are complemented by pointwise displacement rates from accurate positioning (GNSS), projected into the satellite line-of-sight (LOS). We also compare InSAR-derived rate maps and LOS gradients along multiple cross-orogen transects with geologic fault maps, seismicity, and topography. 

The resulting rates describe the kinematics from the Puna Plateau through the Eastern Cordillera to the highly vegetated Subandes, including the frontal Mandeyapecua thrust. They reveal a variety of active processes in the Central Andean backarc: The long-wavelength E–W crustal shortening signal (~1 cm/yr LOS) is overlaid by local processes like inflation at Cerro Overo volcano (~1.5 cm/yr LOS), the dynamics of salars such as the Salar de Arizaro (~0.5 cm/yr LOS), coseismic displacement of ~8 cm associated with the 2020 Mw 5.8 Humahuaca earthquake, and several landslides.