Study On The Methods Of Selective-cut And Adaptive Trend-analysis For Gravity And Magnetic Anomaly Separation

The measured gravity and magnetic anomaly is the superposition of field derived from numerous geologic bodies underground. Accurate inverting and explaining for the data of gravity and magnetic usually need to acquire the field corresponding to the specific geologic body. So this requires the data processing of gravity and magnetic anomaly separation. It is necessary to the gravity-magnetic survey. In general, persons presume that the measured gravity and magnetic anomaly is the sum of the regional anomaly originated from deep geologic bodies and the local anomaly originated from shallow source bodies. Basic on this, there have been come out many methods for separating the regional anomaly and the local-anomaly, such as interpolation cut in spatial domain which is famous to a lot of researchers. Besides, the method of trend-analysis is another popular one. This paper just base on these two methods, and conduct an extensive and detailed study.Firstly, with the help of model data, we systematically analyze the application characteristics and its latent reason of the interpolation cut. The experimental results show that the effect of anomaly separation would be better when the cut radius is in the range of one-fifth to one-twentieth of the local anomaly width. Afterwards, in view of the problem that value vibration and false anomaly occur in the anomaly separations result of the method of interpolation cut, we present a method of selective-cut for gravity anomaly separation. This method selectively cut the embossing local-anomaly, based on the plus-minus character of the half value of the second-order-difference. The tests show that the anomaly separation result is accurate, smooth and no false anomaly.Secondly, considering the drawback that the regional anomaly calculated by the method of trend-analysis is badly affected by the local anomaly, we propose a method of adaptive trend-analysis. This method calculates the regional-anomaly after removing the nodes of local anomaly, so the calculated regional anomaly is little affected of the local anomaly. And the separation result will be more accurate.Lastly, we utilize the measured gravity and magnetic anomaly data at a digging of Tong-Ling to explore the actual application character of the methods for field separation.Some complicated synthetic data examples and measured data examples are used to systemically analyze the application characteristics of the methods for field separation. Comprehensive analysis of these methods shows that the magnetic separation result by the method of interpolation cut will be exact and reasonable, the gravity separation result by the method of selective-cut will be good effect, and the adaptive trend-analysis can effectively reduce the disturb from local anomaly, compared with routine trend analysis when we calculate the regional anomaly.