3-D Analytic Signal in the Interpretation of Total Magnetic Field Data at Low Magnetic Latitudes

The interpretation of magnetic field data at low magnetic latitudes is difficult because the vector nature of the magnetic field increases the complexity of anomalies from magnetic rocks. The most obvious approach to this problem is to reduce the data to the magnetic pole, where the presumably vertical magnetization vector will simplify observed anomalies. However, RTP requires special treatment of North-South features in data observed in low magnetic latitudes due to high amplitude corrections of these features. Furthermore, RTP requires the assumption of induced magnetization with the result that anomalies from remanently and anisotropically magnetized bodies can be severely distorted. The amplitude of the 3-D analytic signal of the total magnetic field produces maxima over magnetic contacts regardless of the direction of magnetization. The absence of magnetization direction in the shape of analytic signal anomalies is a particularly attractive characteristic for the interpretation of magnetic field data near the magnetic equator. Although the amplitude of the analytic signal is dependent on magnetization strength and the direction of geologic strike with respect to the magnetization vector, this dependency is easier to deal with in the interpretation of analytic signal amplitude than in the original total field data or pole reduced magnetic field. It is also straight forward to determine the depth to sources from the distance between inflection points of analytic signal anomalies.