Method for separating gravity and magnetic field in DCT domain

Abstract

The invention belongs to the field of processing of gravity and magnetic data, in particular discloses a method for separating a gravity and magnetic field in a DCT domain, which comprises the following steps: carrying out gridding treatment on two-dimensional discrete gravity and magnetic data obtained by field measurement, and forming regular grid data; converting the grid data into the DCT domain from a space domain, and obtaining a frequency spectrum of original data; setting n different threshold values En, and counting an area An surrounded by all sets, the energy spectrum values of which are larger than En; drawing a logEn-logAn bilogarithmic graph in a rectangular Cartesian coordinate system, using a least square method to fit a plurality of straight-line segments with different slopes, and determining an energy spectrum boundary value of a filter according to the energy spectrum value corresponding to the intersection point of the straight-line segments; carrying out filteringtreatment on the gravity and magnetic field according to the determined energy spectrum boundary value; and carrying out the inverse discrete cosine transform to the filtering result and converting the filtering result into the space domain from the DCT domain to acquire the separating result of the original data. The method of the invention has stronger decorrelation ability, fully considers thespatial self-similarity or multi-fractal characteristics of the gravity and magnetic field, and can effectively separate the gravity and magnetic field from a local field.

Description

technical field [0001] The invention belongs to the field of gravity and magnetic data processing, and in particular relates to a gravity and magnetic field separation method in a DCT domain. Background technique [0002] The separation of regional field and local field is one of the important contents of gravity and magnetic data processing. In the 1950s, the introduction of discrete Fourier transform (DFT), especially the advent of fast Fourier transform (FFT) in 1965, freed gravity and magnetic data processing from complex space domain operations, and also made DFT In-domain filtering methods have become the main method for gravity and magnetic field separation, such as commonly used high-pass and low-pass filters. These filtering methods are often based on the magnitude of the frequency, but in fact the same type of geological bodies will have different frequencies. On the contrary, geophysical fields with the same frequency may not reflect similar geological phenomena,...

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Problems solved by technology

[0004]At present, the application of DCT at home and abroad is mainly limited to the fields of seismic data processing and image compression

In 2005, Zhang Fengxu et al. applied DCT to the gravity and magnetic data processing for the first time, and studied the conventional processing methods such as upward continuation and derivation of the gravity field in the DCT domain, but did not involve the spatial self-similarity or multifractal characteristics of the gravity and magnetic field and the relationship with The related gravitational and magnetic field separation method

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