A modern gravimetric methodology applied to the study of Bolivian Andes

CROVETTO C.- INTROCASO A

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

Año: 2006

0895-9811

In this work we show that gravity anomalies and disturbing earth potential values can be used together to consistently study crustal structures. An example on Bolivian Andes chain supports this proposal. First, we have defined a comparison model with a modern digital elevation model as input signal assuming perfect isostatic balance in Airy’s system for this Andean zone (general assumed tendency). We have evaluated free-air anomalies, Bouguer anomalies and geoid undulations from this theoretical model. Then, using EGM96’s geoid model for Bolivia (real data), we have filtered long and intermediate wavelengths using a sparse Fourier transform method, obtaining residual geoid values (Andean wavelengths), showing a tendency to isostatic balance when compared with isostatic geoid values from our predictive assumed model. With residual geoid values from EGM96 model, we have evaluated free-air and Bouguer anomalies using two methods: equivalent sources techniques and planar Stokes’ formulae. When compared with those from the assumed comparison model, Bouguer anomalies certify the balance already found, while free-air anomalies although less consistent, remark the separation between positive and negative values areas. Results also agree with observed free-air and Bouguer anomalies charts for the zone. We show that geological structures can be studied by means of geoid undulations and topography values without using observed gravity anomalies.