Research On Estimating Source Depth By Power Spectrum

The radially averaged logarithmic power spectrum can estimate the depth of source quickly and roughly without prior information.It has been widely used in magnetic data processing,especially in aeromagnetic data processing.Based on the forward expression of the spectrum of the vertical rectangular prism,the relationship between the power spectrum and the depth of the field source is established by mathematical statistics method.It is a frequency domain inversion method.The power spectrum expression is composed of top depth factor,extension factor,horizontal scale factor and so on.In this paper,the influence of each factor on the power spectrum is studied by controlling variables,and the results show that the inherent decay of horizontal scale factor needs to be modified.In order to solve this problem,by analyzing and summarizing the results of a large number of model depth estimation,the correction method of horizontal scale factor is given,and two practical correction strategies are put forward.Then,according to the different observation conditions in practical application,the effects of polarization,window size,sampling interval and field source deviation from the center of the window on the power spectrum estimation of the depth of the field source are analyzed by model experiments.The selection principle of calculation parameters is summarized.The results of trial calculation and practical application of complex model show that good depth estimation effect can be obtained by using horizontal scale factor correction method on the basis of reasonable selection of calculation parameters.Another important application of the power spectrum method is to reverse the depth of the Curie interface.In this paper,the previous research work in Curie interface is summarized,and on the basis of the existing Curie depth data,a regional field source model of multi-prism combination is established for trial calculation.Through a large number of field source model experiments with variable top depth and variable depth,the selection principles of frequency band,window size and other parameters in Curie depth estimation are summarized.The experimental results of the model show that the power spectrum method can obtain better depth estimation effect in the range of the given model parameters.In practical application,the deformation of area and length is large in large area coordinate projection,which seriously affects the accuracy of sliding window depth estimation.In order to solve this problem,a "zonal sliding" method based on UTM projection is proposed in this paper.On the basis of theoretical analysis and model experimental study,the Curie depth of EMAG2 magnetic anomaly data in the western Pacific region is estimated by using the "zonal sliding" method,and the cordial depth isoline map of the region is obtained.The inversion results have a good correlation with the geological structure and heat flow map of the western Pacific Ocean,and have certain application value.