| In this paper, we mainly use the gravity and magnetic data to identify the border and extract the weak anomalies and then prove it with theoretical models. Finally, we consider the gravity and magnetic data in Qiqihar as the research object, which has complex geological constitution, and then give some geological interpretation. The main parts of my work are as follows:1.We propose a method to determine the boundary by scanning the smallest Lyapunov index on both directions and made a useful attempt. The specific process is as follows:(1) The gravity and aeromagnetic grid data meets in the same line along rows or columns. We select each line as a window, that is, row or column is selected as a single variable time list to calculate the Lyapunov index directly.(2) Divide the data matrix m x n by line to get n rows, and each row can be calculated, that is, there is only one Lyapunov index corresponding to every latitude,which is the same with every longitude according to the column. Two Lyapunov index sequences are attained essentially.(3) We can see from the two Lyapunov index sequences that, every point has only one couple Lyapunov indexes. As we known for the definition of lyapunov indexes, when the two indexes are both the smallest of each sequence, the point should be inflexion of surface or plane location of extremum.2. Usually, link line of inflexions or extremums corresponds with the boundary surface or axes projection on ground of geological properties. To test the validity of the method above, the two theoretical models of step and Horizontal cylinder are established, and the Qiqihar gravity and magnetic data are processed. The result of theoretical model tallied with the location of design, and link line of lyapunov index minimums tallied with the boundary of Great Xing'an Mountains gradient zone.3. In order to extract weak anomalies more Effectively, advantages and disadvantages of the self-autocorrelation filters in gravity and magnetic data processing are summarized. Through testing the established single sphere and multi sphere gravity models, it is found that Baohu Qin's self-autocorrelatioin filter factor could basically eliminate the random noise and could reflect the regional tendency at a certain extent in portrait as well as showing up the existence of anomaly in landscape in 1991.However, it has some disadvantages. For example, the result of the filter is still affected by the regional filed,the weak anomaly extracted is too small and accompanied false anomaly, some of the filter functions are ambiguous and so forth.1D and 2D self-autocorrelatioin filter factors are researched and modified to remedy these drawbacks that extracting local weak anomalies. The specific methods are as follows:(1) Modify 1D self-autocorrelatioin filter factor:by automaticly finding the point whose local residual anomaly was maximum in each line, considering it's value as our reference model and making use of sliding autorelation processing in the whole line. In data processing, we only need to give the filter window K, which should be equal to the radius of the scale of the anomaly maximum, by analyzing the anomaly scale. The result of models is correct, and it does not only reduce the regional effect, but also highlight the weak anomaly. When the data is combined with random noise, it can not be completely healed, and falsehood anomalies distributed inhomogeneous, and falsehood anomalies is bigger on the side where has bigger regional field, and the result is scored by window sliding.(2) Modify 2D self-autocorrelatioin filter factor:we change the coefficient of self-autocorrelatioin function p and the expression of the mean value of the point all around Z(l).2D self-autocorrelatioin filter could only be applied to the case that line space equals to spot space, and the data has to be transformed to a network of square if not; Choosing 3～6 plus the grid distance as the self-autocorrelatioin radius is preferred, in the time the zero isoline could reflect the range of the geologic body well; The improved method has many advantages such as suppressing the random noise at a certain extent, eliminating the impact of background, extracting the weak anomaly, and outlining the boundary of geologic body by the zero isoline; As high saltation points will strongly influence the result, eliminating preprocessing is required.4.To test the effect of modified filter factor, we apply this method to the aeromagnetic data in Qiqihar. The result can well determine the location of every local anomaly, partition the boundary clearly and extract the weak anomaly on the field of strong anomaly basically. However, the random noise could not be eliminated absolutely as the self-autocorrelatioin filter factor does not suppress the random noise well, which will lead to the existence of false anomaly.By comparing matched filtering with self-autocorrelatioin filtering, it shows that the effect of regional filed is small and the local anomaly is independent, and therefore, the processing result could better reflect the distribution of local anomaly. According to the denseness of the weak anomalies, the area is divided into two parts. The first, whose local anomaly is controlled by the regional geological structure and most of the tectonic lines extend along between NE and NNE directions, belongs to the Variscan fold belt of Daxinganling:while the other one belongs to Songnen Plain, where the magnetic filed is stable without obvious anomaly. Because of it's strong and concentrated magnetic anomaly, the aero marked A has some important scientific interests and can be future explored as a prospect area. Finally, the map of structural characteristic lines is drawn.5. Introduce academic knowledge of fractal geometry, the connection of fractal and chaos ore formation, summarize the application of fractal in gravity and magnetic data. Both the fractal dimension and lyapunov index characterize the non-linear system, so the mind that identifying the boundary by Lyapunov index on both directions can be used into fractal, that is, window sliding in fractal can be used for identifying the boundary of geological body, and this is one of my works forward.
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