Reduction to the pole (RTP) is a standard part of magnetic data processing method, especially for large‐scale mapping. RTP operation can transform a magnetic anomaly caused by an arbitrary source into the anomaly that the same source would produce if it is located at the pole and magnetized by induction only. Interpretation of magnetic data can further be helped by RTP in order to remove the influence of magnetic latitude on the anomalies, which is significant for anomalies caused by crust. The solution of RTP in the wave number domain faces a long standing difficulty of instability when the observed data are acquired at low latitudes especially at the geomagnetic equator. We present a new solution to this problem that allows stable reconstruction of the RTP field with a high fidelity at the magnetic equator, combining the reduction to the equator (RTE) and the phase reversal interpretation method for ∆T anomalies at low latitudes. The operation with RTE can transform theoretical magnetic anomalies located at the pole and magnetized by induction only into the observed magnetic anomalies. RTE used in our RTP procedure named SRTE is an absolutely stable potential field transformation. The principle of method is very simple, it can transform the observed magnetic anomaly at geomagnetic equator into the anomaly that would have been measured if the magnetization and ambient field were both vertical. It is a stable RTP operation at geomagnetic equator and performs a high computation speed with a reasonable accuracy. Theoretical models and the practical magnetic field data located at the magnetic equator show that the operator of RTP solution is stable and accurate.
Reduction to the pole (RTP) has played a key role in the interpretation of magnetic anomalies. In order to overcome the unstableness of RTP at low magnetic latitude, there are varieties of methods of RTP. We propose a new method of inversion by probability tomography that allows stable reconstruction of the RTP field with a high fidelity even at the magnetic equator. The inverse model for RTP calculation consists of a set of juxtaposed equivalent prisms. This inversion carries on gradually by imagery of the residual magnetic anomalies and realizes the complexity mapping from the probabilistic model to the geophysical model under the condition of tomography. The processing of inversion does not need to solve linear algebraic equation system. The construction of probabilistic model, inversion for physical properties and appraisal can be organically integrated together to speed up the process of inversion, so that the speed of inverse calculation can be compared with the probability tomography. The computations of the model and practical field data demonstrate the effectiveness of the method that the equivalent source construction offers a stable means for reducing a set of magnetic data to the pole at the equator even with noise.
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