Mapping the disruption of source magnetization depth estimates by near-surface magnetisations

Near-surface magnetisations are ubiquitous across many areas of Australia and complicate reliable estimation of depth to deeper magnetisations. We have selected four test areas in which we use equivalent source dipoles to represent and quantify the near-surface magnetisations. We present a synthetic modelling study that demonstrates that field variations from the near-surface magnetisations substantially degrade estimation of depth to a magnetization 500 metres below the modelled sensor elevation and that these problems persist even for anomalies with significantly higher amplitudes. However, preferential attenuation of the fields from near surface magnetisations by upward continuation proved quite effective in improving estimation of depth to those magnetisations.