Alternative gravimetric methodology for isostatic analyses. An example for Bolivian Andes

In this work we present a new, alternative methodology for performing isostatic studies by means of geoid undulations, excluding the use of measured gravity anomalies. An example on Bolivian Andes is presented as case study. Considering a digital elevation model as input data, a theoretical perfectly isostatically balanced Airy crustal model was constructed for Bolivia. The free-air and the Bouguer anomalies, and the geoid undulations produced by this theoretical model, were directly evaluated by means of three-dimensional integration. The “real” geoid undulations were computed from the EGM96 global geopotential model, and were filtered from long wavelengths by means of a sparse Fourier transform method. The residual “real” geoid undulations were compared with the theoretical geoid undulations for Bolivian Andes, showing a global tendency towards isostatic balance, agreeing with previous results obtained using traditional gravimetry. The free-air and the Bouguer anomalies from the EGM96 residual geoid undulations were also evaluated and then compared with the anomalies produced by the theoretical model. The Bouguer anomalies support definitely the results obtained using the geoid undulations while the free-air anomalies, although less consistently, showed the same global tendency.