Magnetic data analysis at low latitudes using magnitude transforms

Magnitude transforms include magnitude magnetic anomalies (MMA), their gradients and Laplacians. They can be calculated from the total magnetic anomalies or other component anomalies. Magnitude magnetic anomalies have a space distribution different from that of the component anomalies. Their values are non-negative and their respective patterns are similar to the positive gravity anomalies. Magnitude transforms are an effective tool for magnetic data analysis due to their simplified pattern and direct correlation with the space location of the source. They have advantages over the traditionally used reduction-to-the-pole (RTP) transform, especially at low magnetic latitudes. The calculation of magnitudes of the anomalous field requires the total field data to be transformed into the component anomalies, while the reduction-to-the-pole transform also includes a rotation of the magnetization vector, the orientation of which is usually assumed. For equal latitudes, the transfer functions of component-component transforms in the frequency domain show better stability than the component-component-rotation transfer function. This is illustrated by a comparison of analytical expressions, and synthetic models of magnetic fields. The Dixon seamount case shows the possibilities for an improved data analysis and more confident source recognition at low latitudes using magnetic transforms.