Study Of Extracting Multi-frequency Information Of Magnetic Abnormity And Its Application

In geological work, differentiating lithology is one of the important tasks for ground high precision magnetic survey. It is worthy of studying how to differentiate lithology using different characteristic magnetic abnormity in horizontal direction. We research on extracting multi-frequency information of magnetic abnormity and its application, starting from this aspect.In this paper, the conception of"multi-frequency magnetic abnormity"is put forward on the base of previous scholar's work. We also put forward the idea to differentiate frequency using small wave method and interpolating cut method. After the research on three groups of theoretical model data, it is proved that multi-frequency information of magnetic abnormity really exists. It's also proved to be possible to differentiate frequency of magnetic abnormity.We also summarize the filter parameter using small wave and interpolating cut method to differentiate frequency.We have developed a series of programs for extracting multi-frequency information of magnetic abnormity, such as small wave filter, interpolating cut filter, 2D any number and any shape horizontal column magnetic abnormity modeling, magnetic data settling, basic ground magnetic referential field calculating, section and plane map plotting.In this research work, we introduce the concept of"coefficient of variation"into the statistic of magnetic sample parameter for the first time and discuss its physical meaning. The result is: there is direct connection between high frequency magnetic abnormity and sample's over big coefficient of variation in three directions; there is some connection between middle frequency magnetic abnormity and some lithology's over big magnetic coefficient of variation.We also discuss the relationship between the different frequency magnetic abnormity and high back ground of geological lithology and geochemical element using integrated, large area, enormous practical data in this paper. We get such results:1. Information doubly increases after differentiating frequency and a lot of information which could not be got from original data (including normal data processing) can be gained.2. Different frequency information have different macro characters after differentiating frequency and more information can be got if more frequencies are differentiated.3. It is not true that one lithology only correlate with one frequency magnetic abnormity. Therefore, the similar responses to one lithology for different frequencies mean that similar frequencies lithology have similar characters.4. Different differentiating methods are not the main factors which decide the result for interpolating cut and small wave method. The results get from interpolating cut method and small wave method are similar.5. Differentiating method and technical parameter are not the critical factors which decide the frequency of extracting data. Different data have different frequency character using the same differentiating method.6. Lots of new information can be got if 4 or 5 frequencies are differentiated. The workload(plotting and manual analysis) and reference of similar frequency character difference should be considered if more frequencies are differentiated.7. Manual analysis after information being extracted is one step which should be paid much attention to in abnormity interpretation as normal magnetic abnormity interpretation.8. Coefficient of variation can be choose as examine parameter for the study of the contrast between asymmetry of different magnetic intensity lithology themselves and asymmetry of one another.9. Differentiating magnetic abnormity can differentiate different lithology. The effect is especially obvious for the lithology which can not be differentiated by middle and weak original magnetic data.10. There is much clearer corresponding relationship between magnetic abnormity after differentiating and geochemical map.