Study On The Separation Of Gravity And Magnetic Potential Field And Boundary Recognition Method

With the development of modern industry, the degree of mineral explorationis increasing and looking to the quality of shallow deposits has been difficult. It needs to provide strong technical support for deep mineral exploration. The gravity and magnetic method is an important branch of application of geological exploration and mineral for geophysical technology. It plays an important role for realizing the effective separation of underground geological bodiesanomaly and for completing geological body distribution, location, occurrenceand the geological interpretation. At the same time, because the gravity and magnetic method has the advantages of low cost, high efficiency, wide coverage, the measurement process without geographical constraints and other advantages, it has become an important and irreplaceable method for geophysical exploration.The actual gravity and magnetic data obtained is caused by the different underground geological factors of superimposed anomaly. It is the comprehensive reflection for different buried depth and scales of geological bodyunderground. For analyzing the superimposed anomaly, on the one hand, it can separate the potential field data and obtain the anomaly with different buried depth and scales for examing, and further research. On the other hand, it can enhance the edge of gravity and magnetic anomaly and realize the rapid tectonic division as well as anomaly, include completion of the geological anomaly range division.Based on the potential field data processing technology research, this thesis studies the traditional potential field separation and the anomaly edge enhancement technology. It studies the multi-scale curvelet decomposition theory deeply and realizes the separation of geological bodies with different scalesand depth. It avoided the shortcomings of the traditional "dichotomy" method based on the analysis on anomaly in different scales. For alleviating the obvious deformation problem of boundary shape after enhancement and achieving the effect of noise cancellation, the local enhancement method based on partial differential equations is promoted. To enhance the deep buried weak anomaly boundary and realize the enhancement equilibrium among gravity and magnetic anomaly with different depth, the normalized sobel edge enhancement method and the multiplication of morphology erosion and dilation methods are proposed to increase the weak and strong anomaly boundary at the same time, to achieve different depth anomaly boundary enhancement. In this thesis, the automatic extraction of anomaly boundary method based on canny operator is studied and an improved canny edge detection algorithm is proposed, which is more suitable to the actual data of continuous edge detection. To be specific, the research results mainly include the following:1、In order to avoid the question based on traditional "dichotomy" and to realize effective separation of different depth and scale of geological anomaly in multi scales, the multiscale transform analysis and the denoisingmethod based on Curvelet is studied. It can be concluded that the multi scale decomposition reconstruction results of each layer based on Curvelet transformation could corresponding to the different scales of geological anomalies. Because the geological body with large range and deeply buried usually has the large scale and gentle abnormal distribution, and the geological body with small and shallow buried usually has small and dramatic changes abnormal distribution. Through the model test, it can be concluded that the abnormal distribution with different depth and range could be decomposed based on the multi scale analysis ability of the Curvelet transformation. The results show that it is better than the result from the cutting method and can use to provide more adequate information for the rational interpretation of the physical meaning of the geological body.2、The weak gravity and magnetic anomalies enhancement method is studied through the partial differential equation based on local region processing. It ease the abnormal edge deformation problem after enhancement. In order to complete the identification of the anomaly boundary with different depth, the normalized sobel enhancement method is proposed. It can be enhancement balanced for the weak and strong boundary. For the same purpose, multiplication of morphology erosion and dilation methods are proposed to increase the weak and strong anomaly boundary at the same time. Because the morphology erosion could be used to remove the weak noise and the morphology dilation could be used to remove the strong noise. The influence of the noise is removed and the enhancement is balanced. The edge after enhancement is more continuous based on the method proposed in this thesis. The processing results based on the above enhancement method show that it can realize reliable detection of anomalous boundary.3、In order to realize the rapid tectonic division and the anomalydelineation, it need to achieve the boundary detection and location of abnormal. However, the edge of the geological boundary is usually fuzzy or expanded due to the influence of the size of filter after enhancement and it is difficult to accurately represent the real boundary around the Geological body. Therefore, a method of automatic extraction algorithm based on the canny operator is improved. By introducing the anomalous boundarygradient direction, and the feature that edge points usually has the characteristics of continuous and slow variation on gradient direction. The proposed method is more suitable to get the continuous edge detection result from the actual data and provides a powerful support for automatic, rapid, accuracy abnormal boundary localization.The gravity and magnetic anomaly data is processed based on the method proposed in this thesis, and it is explained further combined with the characteristics of geological structure and lithologic distribution characteristics of the area. Focusing on the scale of 1:2 million high-precision ground magnetic survey data in Yongsheng watershed in copper,Yunnan prospect. Using the method of curvelet decomposition of this paper proposed, the multi-scale field separation is realized. The results show that, the method proposed has better multi-level fine analysis ability than the continuation method and cutting method.It proves that the method has a good application prospect in the gravity and magnetic field separation and interpretation. Further, the regional gravity and magnetic data were processedwith normalized sobel edge enhancement and morphological processing method proposed in this thesis. It increase the weak and strong anomaly boundary at the same time.It realized the extraction of the geological body boundary based on the improved canny algorithm proposed in this thesis, and the characteristics of geological structure in the area and the lithologic distribution characteristics is interpretated.