Issues related to determination of the horizontal centre of magnetization

Abstract

The direction of magnetization of a compact source causing a magnetic field anomaly can be found without concern for the details of its shape using magnetic moment analysis (MMA). This provides assistance in the successful inversion of magnetic anomalies due in part to remanent magnetization of unknown direction. However, the success of MMA is dependant on the analysis being positioned appropriately over the horizontal centre of the source body. MMA itself can derive an estimate of the horizontal centre of magnetization and in this presentation we investigate the conditions for stable convergence of an iterative solution that progressively steps the analysis to a revised horizontal centre of magnetization. We find that reliable magnetization directions can be recovered for grid widths down to twice the source depth and less. One, or at most two iterations of the analysis should locate the horizontal centre of magnetization over a compact source to within 5% of its depth and with a resulting uncertainty in magnetization direction of the order of 5°.