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K. KUNARATNAM 《Geophysical Prospecting》1981,29(6):883-890
The magnetic anomaly due to a uniformly magnetized vertical rectangular prism and that due to an arbitrary structure which can be divided into a number of such prisms are expressed in forms suitable for rapid computation. Both two-dimensional and three-dimensional cases are considered. The simplified expressions will find use in interpretation techniques where repeated computations have to be made of the anomaly due to prisms as in automated fitting of prism anomalies to observed magnetic anomalies using non-linear optimization techniques or related methods. 相似文献
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Formulae of the energy spectrum and autocorrelation function have been derived for magnetic anomalies due to four classes of bodies which can be represented in turn by (a) poles, (b) line of poles, (c) dipoles and (d) line of dipoles. The effects of the depth and dimensions of the magnetized sources on the spectrum and the autocorrelation function have been studied. In the case of the dipole models, the orientation of the polarization vector casts a significant influence on the characteristics of the two functions. In all cases, however, the functions change in size and shape as the inclination and declination of the geomagnetic vector are varied. 相似文献
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P. VALLABH SHARMA 《Geophysical Prospecting》1967,15(2):167-173
A nomogram is presented which enables evaluation of the components of magnetic attraction of a homogeneous finite rectangular prism, and of gravitational attraction due to a uniform rectangular lamina. In practice any three-dimensional body could be approximated by a number of right rectangular prisms of varying dimensions governed by the shape of the body. The magnetic attraction of the whole body is then obtained by numerical summation of the effects of the constituent prisms. For evaluating the gravitational effect, the cross-section of the body corresponding to each elevation contour is approximated by a number of rectangular laminae (or by a stepping polygon) the attraction of which can be determined with the aid of the same nomogram. The total gravitational attraction of the body is obtained by a process of graphical integration along the vertical axis. 相似文献
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Rao , K. G. C. and D. N. Avasthi , 1973, Analysis of the Fourier Spectrum of the Gravity Effect Due to Two-Dimensional Triangular Prism, Geophysical Prospecting 21, 526-542. Fourier Transform of the theoretical gravity effect due to a two-dimensional isosceles triangular prism has been derived. Evaluation of the model parameters from the analysis of the Fourier Spectrum has been outlined. Application of this method to synthetic gravity anomalies is shown. 相似文献
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小波变换多尺度分析是位场分解的有益工具.离散二维小波变换产生的低阶小波细节具有尺度不变的特征,它们不随小波变换的总阶数改变,而总阶数的增加仅增加高阶小波细节的个数和改变最后的高阶逼近.因此,用小波变换分解重力异常时,可根据地质目的来组合小波细节,从而实现有地质意义的异常分解.实验表明,用小波变换分解的重力异常小波细节,同样起到功率谱分解的作用,用分解之后的小波细节功率谱可以精确确定场源的埋深.中国大陆科学钻探场地的重力异常分解给出局部异常分解的典型例子. 相似文献
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The Fourier transform formula for a two-dimensional fault truncating a horizontal bed at an arbitrary angle of inclination is derived. The amplitude spectrum of the Fourier transform is found to give information about the depth to the top of the upper part of the faulted bed and the inclination of the fault-plane. Under suitable conditions the thickness and the displacement of the bed involved can be obtained. With actual field data, these transforms can be obtained at discrete points by a Fourier analysis of the gravity anomaly. A field example from the Logan fault area near Montreal, Que., Canada, is given. 相似文献
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The development of an alkali vapour vehicle borne magnetometer providing very high resolution and a high sampling rate has called for reconsideration of interpretation procedures. With continuous profiling at ground level, the close proximity to near surface structures requires that the precise interpretation of geological boundaries be of paramount importance. Rapid digital recording also demands efficient data processing. Both these requirements can be met by the method described. Essentially the method reduces to a simple Hilbert transform of the magnetic profile. The calculation provides an extremely well defined position of the contact and accurate specification of the dip, strike, depth of overburden, and magnetic susceptibility parameters. Particular advantages are tolerance to high frequency noise, independence from a predetermined origin and baseline, and freedom from subjective judgements. 相似文献
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本文将均质的任意二维、三维物体位场的波谱解析表达式的研究成果推广到变密度、变磁化强度的更一般的情形。对密度差随深度呈指数函数衰减或线性变化的模型,获得了任意倾斜多边形质量面、斜平行六面体以及一般的多面体等形体的重力谱的解析表达式。它们的结构与均质体相应表达式一样简单,易于计算。以上结果表明,在很一般的条件下,位场波谱具有指数函数和的形式。 相似文献
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本文将均质的任意二维、三维物体位场的波谱解析表达式的研究成果推广到变密度、变磁化强度的更一般的情形。对密度差随深度呈指数函数衰减或线性变化的模型,获得了任意倾斜多边形质量面、斜平行六面体以及一般的多面体等形体的重力谱的解析表达式。它们的结构与均质体相应表达式一样简单,易于计算。以上结果表明,在很一般的条件下,位场波谱具有指数函数和的形式。 相似文献
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本文从勘探地球物理的实际需要和特点出发,探讨了重磁位场解析延拓的数学提法,给出一套较为实用的数值解法。所论述的原理、方法适用于三维空间任意起伏地形条件下的重磁位场曲化平计算,可做“上延拓”计算,也可做“下延拓”计算。在一个比较复杂的理论模型上所做的方法检验表明“上延”和“下延”都取得了较好的效果。 相似文献
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利用虚磁荷的概念作磁场向上延拓,首先是提出的。他研究了地形水平的情况.设观测面上某点Q(α,β,γ)的单位面积虚磁荷的量为 m=Za(α,β,γ)/2π. (1)Za(α,β,γ)为Q(α,β,γ)点实测的垂直磁异常,则向观测面上半空间任一点P(x,y,z)延拓的公式为 相似文献
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利用虚磁荷的概念作磁场向上延拓,首先是提出的。他研究了地形水平的情况.设观测面上某点Q(α,β,γ)的单位面积虚磁荷的量为 m=Za(α,β,γ)/2π. (1)Za(α,β,γ)为Q(α,β,γ)点实测的垂直磁异常,则向观测面上半空间任一点P(x,y,z)延拓的公式为 相似文献
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本文从勘探地球物理的实际需要和特点出发,探讨了重磁位场解析延拓的数学提法,给出一套较为实用的数值解法。所论述的原理、方法适用于三维空间任意起伏地形条件下的重磁位场曲化平计算,可做“上延拓”计算,也可做“下延拓”计算。在一个比较复杂的理论模型上所做的方法检验表明“上延”和“下延”都取得了较好的效果。 相似文献
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The gravity effect of an infinite horizontal trapezoidal prism is derived and its Fourier spectrum is analyzed so as to yield information about four parameters of the causative structure, namely the depths to the upper and lower surfaces, width of the upper surface, and the inclination of the sides. In order to test the applicability of the method, synthetic data are constructed by digitizing the theoretical gravity effect. Subsequently, the corresponding Discrete Fourier Transform (DFT) is obtained. The parameters evaluated from the DFT are observed to be sufficiently close to the chosen values. 相似文献
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P. J. GUNN 《Geophysical Prospecting》1972,20(4):860-871
Consideration of the spectral representation of gravity and magnetic fields shows the field to be the result of the convolution of factors depending on the parameters of the field. Wiener filters, calculated using model transformations, provide an optimum method for altering these factors and hence effecting field transformations. 相似文献