Investigation of the Roughness of the Australian Gravity Field Using Statistical, Graphical, Fractal and Fourier Power Spectrum Techniques

As one of the world’s oldest continents, Australia has experienced a complicated geological and geomorphological history. As such, the gravity field of Australia behaves differently to that reported in other countries. This paper investigates the relative roughness of three types of gravity anomaly (freeair, refined Bouguer and topographic-isostatic) using statistical and graphical comparisons, power spectrum analysis, and the Hurst fractal technique. Gravity and height profiles in the Hamersley Ranges, central Australia and the Snowy Mountains, which exhibit some extreme features, have been selected to compare these methods. The statistical comparisons are the most informative tools for measuring the relative roughness of the gravity field. Also, not one of the free-air, refined Bouguer or topographic-isostatic gravity anomaly is consistently the smoothest type in Australia, which is due to a combination of a lack of accurate topographic density information and a relatively long-wavelength topography so that the terrain correction cannot always smooth the computed gravity anomalies. It is recommended that the smoothest type of gravity anomaly in each area be used to grid gravity data prior to geoid computation.