Investigating Moho depth variations beneath the South American continent using geodetic constraints

SUMMARY The South American continent (SAC), a region of pronounced geodynamic and hydrological activity, exhibits crustal deformation and gravity field anomalies driven by the interplay of tectonic forces and surface/subsurface mass redistribution. While previous studies have mainly focused on gravity changes driven by terrestrial water storage (TWS), mass variations of the solid Earth remain inadequately addressed. In this study, we resolve deep-seated mass transport Gravity Recovery and Climate Experiment (GRACE) satellite gravimetry, hydrological model outputs, GPS-derived vertical crustal motions and glacial isostatic adjustment (GIA) correction. Our results reveal an internal mass variation of 0.21 ± 0.45 cm yr−1 in equivalent water height (EWH), independent of surface hydrological contributions. Interpreting this signal as predominantly driven by crust–mantle boundary (Moho) displacements, we estimate an average Moho depth uplift rate of 0.37 ± 0.80 cm yr−1 across SAC, based on the crust–mantle density contrast. The Moho interface depth variations exhibit significant spatial heterogeneity. Through uncertainty analysis, four distinct regions (A, B, C and D) are identified: Region A exhibits Moho uplift and Region B exhibits subsidence, with part contributions from the isostatic adjustment. Key uncertainties in these estimates stem from sedimentation effects and the accuracy of current observations or models. Subsidence in Region C and uplift in Region D are related to the co-seismic and post-seismic effects of the 2010 Chile earthquake. These findings underscore the significance of solid Earth mass flux in active continental regions and unravel the mechanisms governing crust–Moho mass redistribution.