Towards automated mapping of depth to magnetic basement ? examples using new extensions to an old method

Abstract

The Euler method of automating depth to source from potential field data has undergone resurgence in popularity, with several new extensions to the method developed. Perhaps the most revolutionary of these provides a solution of the structural index as part of the inversion process. Previously, structural index was a required input parameter. Many solutions are generated with the Euler method, and care is used to select the most appropriate. In some cases, accuracies of depth estimates within ±15% of depth of actual source below acquisition height are achieved. Examples of Euler depth results from across three representative areas of Australia are used to demonstrate the utility of the method. Data are presented by several methods, including full 3D visualisation, which allows the solutions to be integrated with other data and inversion results. A depth-to-basement map of the Springvale 1:250 000 map sheet area in Queensland has previously been generated using the Naudy technique, and those results provide a useful comparison with depths derived using the Euler method. A small area in the eastern Yilgarn, Western Australia, contains an elongated sedimentary basin overlying shallow basement cross-cut by numerous dykes and faults. The magnetic expression of basement can be traced from near-surface to a few hundred metres depth under basin cover. This is a good test of the method for providing estimates along the incline from outcrop to increasing thickness of cover. Basement to the eastern Gawler Craton (Olympic sub-domain) lies under several hundred metres of cover, and Euler depth estimates for this area are also examined.