50 years of steady ground deformation in the Altiplano-Puna region of Southern Bolivia

The Altiplano Puna Volcanic Complex of the Central Andes is host to a ~150 km wide, quasi-circular ground deformation anomaly centered on Uturuncu volcano (Bolivia). The precise onset and duration of this deformation is unclear, but geomorphologic studies bracket its initiation at less than a few hundred years ago. Here we report on the deformation history over a ~50 year period by deriving orthometric height changes from leveling and GNSS observations at 53 benchmarks along a regional leveling line that crosses the deformation anomaly. The comparison of InSAR LOS and LOS-projected orthometric ground velocities in a common reference frame reveal central uplift extending to ~35 km from Uturuncu at a maximum orthometric rate of 1.2 cm yr^-1, and peripheral subsidence, at a maximum rate of 0.3 cm yr^-1 to ~60 km from Uturuncu. This pattern is consistent with the spatial extent and average rate of deformation observed by InSAR. Our interpretation of the data is that long-wavelength ground uplift at Uturuncu has likely occurred at a quasi-constant rate for at least half a century. This study bridges the observational timespans between modern satellite geodetic observations (up to a few decades) and geomorphological observations (few centuries and longer) of the recent deformation history of the continental crust in the Central Andes and adds to a select group of case studies of quantifiable long-term volcano deformation world-wide.