Inversion Of Magnetic Gradient Tensor And Example

The magnetic gradient tensor method is one of the important development direction of magnetic prospecting. By using derivatives of three component of magnetic field, it can be used in exploration and interpretation. With development of superconducting magnetometer and multiple magnetic flux measurement device, direct measurement of magnetic gradient tensor becomes possible. Compared to the traditional magnetic prospecting, magnetic gradient tensor can provide more information.In addition, magnetic gradient tensor has more advantages than traditional magnetic anomaly, it is a potential fields, with the property of symmetry and traceless, common processing method of potential field, such as continuation, can be used directly to process the data of magnetic gradient tensor, and influence of the direction of the earth’s magnetic field effects have been relatively small. Gradient tensor measurements can improve magnetic method in the measurement of interpretation, especially in the area which magnetic abnormal is twisted by remanent and low latitude magnetization.Magnetic gradient tensor inversion, compared with the traditional magnetic anomaly inversion, and better resolution, and magnetic gradient tensor has nine components, when we obtain these components, we can achieve joint inversion using the weighted terms in the objective function. The joint inversion contains more information theoretically, so it has better definition of the structure, shape, position and other factors of the abnormal body.The distribution of the anomalies under the underground can be obtained by using the appropriate inversion method. The inversion method we used is preconditioned conjugate gradient method. The preconditioned conjugate gradient method can improve the stability and iterative efficiency than usual conjugate gradient method, so ti becomes one of the mainly inversion method in geophysical potential field inversion. According to the character of the magnetic gradient tensor, several constraint factors are addicted in the inversion, including depth constraint factor, the sparseness constraint factor, we hope to improve the stability and resolution by them.Magnetic gradient tensor has five independent components. Through the experiment, we found that the inversion of each single component of can make a certain effect, but because the kernel functions of each components vary, the inversion results are different, and this is not conducive to geological interpretation. After joint inversion of multiple components, the effect of the combination is more ideal, and the combination model has higher resolution in the deep anomaly. These results also prove the validity of the inversion.Because of the limited conditions, there are also many deficiencies, and in the end of the article, the conclusion and suggestions are given, hoping to inspire people who continue to work in this aspect.