Gravity map of Brazil: 1. Representation of free‐air and Bouguer Anomalies

Abstract

Gravity data of Brazil were processed to obtain continental scale free‐air and Bouguer anomaly maps for a large segment of the South American plate. Gravity measurements are referred to the International Gravity Standardization Net 1971 and the anomalies are calculated using Geodetic Reference System 1967 and 2.67 g cm−3 for Bouguer reduction. In the calculation of the gravity anomalies, information used included geopotential model, topography, geoidal heights, and astrogeodetic deviation of the vertical. Depending on the availability and distribution of land gravity data, various regions have been classified as complete, incomplete, or empty. In complete regions, the gravity field is represented by 0.5° × 0.5° mean free‐air and Bouguer anomalies which were computed from observed gravity data only. In incomplete regions, mean anomalies in empty 0.5° × 0.5° blocks were computed from nearest known mean anomalies, by least squares collocation. Regions totally devoided of gravity data had the gravity field calculated by least squares collocation using all available geodetic data. The gravity map obtained using this approach allows to identify the major gravity anomalies with dimensions greater than 100 km. Such anomalies are mainly caused by intracrustal density variations of geological and tectonic interest.