Complete spherical Bouguer gravity anomalies over Australia

Abstract

We have computed complete (or refined) spherical Bouguer gravity anomalies for all 1,095,065 land gravity observations in the June 2007 release of the Australian national gravity database. The spherical Bouguer shell contribution was computed using the supplied ground elevations of the gravity observations. The spherical terrain corrections, residual to each Bouguer shell, were computed on a 9 arc-second grid (~250 m by ~250 m spatial resolution) from a global Newtonian integration using heights from version 2.1 of the GEODATA digital elevation model (DEM) over Australia and the GLOBE and JGP95E global DEMs outside Australia. A constant topographic mass-density of 2670 kg/m3 was used for both the spherical Bouguer shell and spherical terrain correction terms. The difference between the complete spherical and complete planar Bouguer gravity anomaly exhibits an almost constant bias of about -18.7 mGal over areas with moderate elevation changes, thus verifying the planar model as a reasonable approximation in these areas. However, the results suggest that in mountainous areas with large elevation changes, the complete spherical Bouguer gravity anomaly should be selected in preference over the less rigorous complete planar counterpart.