Estimation of Magnetization Direction over Wide Sheets Illustrated with a Case Study of the Earoo Magnetic Anomaly, Western Australia

Single profile analysis across locally planar structures such as the edges of a wide sheet cannot resolve the 3D magnetization vector but we show that from two or more profiles across differently trending edges the magnetization is uniquely defined as the intersection of possible directions for each profile. This analysis is partially supported by analysis of edge profiles over the Earoo sill of Western Australia. However, practicality of the analysis is restricted by local complication of the sill edges. We obtain more robust estimates of source magnetization direction from 3D inversion of a nearby smaller and simpler anomaly and of the well-defined northeastern section of the Earoo anomaly. These magnetization directions are consistent with the magnetization being a vector resultant of induced magnetization and a stronger remanent magnetization of previously measured direction.