The Interpretation of Magnetic Anomalies Due to Dykes*

Bruckshaw, J. M.; Kunaratnam, K.

doi:10.1111/j.1365-2478.1963.tb02049.x

Cited by 33 publications

(13 citation statements)

References 1 publication

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“…These values are in a good agreement with estimates by the master curves of From measurements of the vertical field on the same line we obtained: Bruckshaw & Kunaratnam, 1963. h, = 3.7m; b = 3-6m.…”

Section: Interpretation Of Measurements Of Dykessupporting

confidence: 80%

Interpretation of One-dimensional Magnetic Anomalies by Use of the Fourier-transform

Guðmundsson

1966

Geophys J Int

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It is proved that the modulus of the Fourier-transform of the magnetic anomaly of a two-dimensional magnetized body is determined by two parameters less than those determining the anomaly itself. This is true for any component of the field.A method is developed to calculate estimates of the Fourier-transform from a limited amount of data and actual examples are given to demonstrate how this can be used in interpretation of magnetic anomalies. The method uses all the information there is in a record about the shape and depth of a magnetized body and concentrates it into a few values. It also provides a convenient way of investigating the amount and nature of the noise.

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Section: Interpretation Of Measurements Of Dykessupporting

confidence: 80%

Interpretation of One-dimensional Magnetic Anomalies by Use of the Fourier-transform

Guðmundsson

1966

Geophys J Int

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“…The model is frequently used in magnetic interpretation to find the depth and the width of a class of geologic structures. Several graphical methods have been developed for interpreting magnetic anomalies due to dipping dikes (PETERS, 1949;COOK, 1950;WERNER, 1953;HUTCHISON, 1958;GAY, 1963;BRUCKSHAW and KUNARATNAM, 1963;GRANT and WEST, 1965;RAO et al, 1967;KOULOMZINE et al, 1970;RAO and MURTHY, 1978; and many others). However, most of these methods use a few characteristic points and distances, nomograms and standardized curves to determine the model parameters.…”

Section: Introductionmentioning

confidence: 99%

A Least-squares Window Curves Method for Interpretation of Magnetic Anomalies Caused by Dipping Dikes

Abdelrahman

Abo-Ezz

Soliman

et al. 2007

Pure appl. geophys.

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We have developed a least-squares method to determine simultaneously the depth and the width of a buried thick dipping dike from residualized magnetic data using filters of successive window lengths. The method involves using a relationship between the depth and the half-width of the source and a combination of windowed observations. The relationship represents a family of curves (window curves). For a fixed window length, the depth is determined for each half-width value by solving one nonlinear equation of the form f (z) = 0 using the least-squares method. The computed depths are plotted against the width values representing a continuous curve. The solution for the depth and the width of the buried dike is read at the common intersection of the window curves. The method involves using a dike model convolved with the same moving average filter as applied to the observed data. As a result, this method can be applied to residuals as well as to measured magnetic data. Procedures are also formulated to estimate the amplitude coefficient and the index parameter. The method is applied to theoretical data with and without random errors. The validity of the method is tested on airborne magnetic data from Canada and on a vertical component magnetic anomaly from Turkey. In all cases examined, the model parameters obtained are in good agreement with the actual ones and with those given in the published literature.

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“…It has been fairly widely used in slightly different forms (Gay 1963;Bruckshaw & Kunaratnam 1963;Bott, Smith & Stacey 1966).…”

Section: Field Pointmentioning

confidence: 99%

Computation of the Magnetic Anomalies Caused by Two-Dimensional Bodies

Bott¹

1969

Geophys J Int

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The magnetic anomaly of a two-dimensional body of uniform magnetization and arbitrary shape can be expressed compactly in terms of the vertical and horizontal derivatives of the corresponding gravity anomaly and an angle p which incorporates both the direction of magnetization and the direction in which the observed magnetic anomaly component is measured. The formula is useful for computing families of curves. By an extended use of the formulation, computation of the conjugate harmonic function to the observed magnetic anomaly makes it possible to compute the anomaly for different values of p without knowledge of the shape of the body. The simplicity of the formulation cannot be extended to bodies of three-dimensional shape but computational short cuts are nevertheless available. The basic formulaIspir & KolCak (1969) have described a useful short cut in computing families of magnetic anomaly curves for two-dimensional bodies. A compact formula of similar type which relates the magnetic anomaly to the derivatives of the gravity anomaly is given here.The formula presented is most obviously useful for calculating families of magnetic anomaly curves over two-dimensional bodies with minimum computational effort, by computer or otherwise. It is a somewhat more general and more simple formulation than that given by Ispir and Kokak. It gives a much simplified approach to the evaluation of analytical expressions for magnetic anomalies caused by geometrical two-dimensional bodies, based only on differentiation of the corresponding gravity anomaly formulae. It also provides a useful starting point in the development of direct methods of magnetic interpretation, and is particularly well suited to the application of complex variable to interpretation theory.Let us consider a magnetic anomaly component produced by a two-dimensional body of uniform magnetization and arbitrary cross-section (Fig. I). The horizontal x-axis is chosen to be perpendicular to the strike of the body and lies entirely above the body. The y-axis points vertically downwards and the z-axis is parallel to the strike. Let the magnetization be J(J,, J,, JJ, its dip I,, its azimuth o r , measured from the x-axis in either sense, and the unit vector in the direction of the component of magnetization in the xy-plane m(cos p, sin p). Let the magnetic anomaly A(x, y ) be measured in the direction F(F,, F,,, FZ). 251

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The Interpretation of Magnetic Anomalies Due to Dykes*

Cited by 33 publications

References 1 publication

Interpretation of One-dimensional Magnetic Anomalies by Use of the Fourier-transform

Interpretation of One-dimensional Magnetic Anomalies by Use of the Fourier-transform

A Least-squares Window Curves Method for Interpretation of Magnetic Anomalies Caused by Dipping Dikes

Computation of the Magnetic Anomalies Caused by Two-Dimensional Bodies

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