SOME COMPUTING TECHNIQUES FOR STORAGE, RETRIEVAL AND INTERPRETATION OF GRAVIMETRIC DATA

Abstract

Gravity coverage of South Australia, with stations on a grid of approximately 7 km, is almost complete. A project aimed at computer-storage, retrieval and utilization of these data has been under-way within the Geophysics Division of the South Australian Department of Mines for two years.

The storage and retrieval system has been adapted from one developed for gravity data by the Bureau of Mineral Resources. Two data files have been established using this system. The first contains all data from individual surveys stored as a retrievable block on the file. The second contains all gravity data recorded on each 1:250,000 scale published map sheet within the State.

Experimental analysis of digitized gravity data from the Great Artesian Basin in South Australia has been undertaken using standard anomaly-separation techniques. A published set of grid operators has been used as the coefficients for each analysis. These coefficients, which are designed for upward and downward continuation and long and short wavelength filtering of potential fields, have each been applied to the test data with various grid spacings. Computer presentation of results allows quick evaluation and comparison of each operator set. Results obtained are suitable for qualitative examination and in the examples chosen indicate limits of intracratonic basins and some detail within them. The nature of this information depends on the grid spacing and operator used. Large amplitude anomalies which cover a considerable area and are due to basement features become more apparent than on the Bouguer anomaly data. An estimate of depth to major density discontinuities has been obtained.

Future aims of the project are: (i) processing of raw data files to prepare and update integrated Bouguer anomaly maps using more accurate density information for the Bouguer correction, and (ii) preparation of processed maps on a statewide basis to aid interpretation of the tectonic and basin framework of the State of South Australia.