COMPUTATION OF GRAVITY AND MAGNETIC ANOMALIES DUE TO INHOMOGENEOUS DISTRIBUTION OF MAGNETIZATION AND DENSITY IN A LOCALIZED REGION

Geophysics ◽  
1977 ◽  
Vol 42 (3) ◽  
pp. 602-609 ◽  
Author(s):  
B. K. Bhattacharyya ◽  
K. C. Chan
Keyword(s):  
Rock Mass ◽  
Physical Property ◽  
Magnetic Anomalies ◽  
The Body ◽  
Inhomogeneous Distribution ◽  
Uniform Magnetization ◽  
Gravity And Magnetic ◽  
First Vertical Derivative ◽  
Analytical Expressions ◽  
Distribution Of Magnetization

Analytical expressions in the form of a convolution of two functions have been derived for the gravity and magnetic anomalies due to inhomogeneous distribution of magnetization and density in a localized region. These expressions show explicitly that the anomalies are completely determined by the divergence of magnetization and the first vertical derivative of density. It is thus analytically established that when a body with uniform magnetization or density is considered, the impulsive change in the physical property of the rock mass at the boundary of the body is responsible for generating an anomalous magnetic or gravity field. These properties are utilized to derive efficient algorithms for computing gravity and magnetic anomalies. An example is given to demonstrate the usefulness of the derived algorithm in computing the anomaly due to magnetization of an irregularly shaped topography.

A DIRECT COMPUTATION OF GRAVITY AND MAGNETIC ANOMALIES CAUSED BY 2- AND 3-DIMENSIONAL BODIES OF ARBITRARY SHAPE AND ARBITRARY MAGNETIC POLARIZATION BY EQUIVALENT‐POINT METHOD AND A SIMPLIFIED CUBIC SPLINE

Geophysics ◽  
1977 ◽  
Vol 42 (3) ◽  
pp. 610-622 ◽  
Author(s):  
Chao C. Ku
Keyword(s):  
Arbitrary Shape ◽  
Gaussian Quadrature ◽  
Magnetic Anomalies ◽  
Cubic Spline ◽  
The Body ◽  
Point Method ◽  
Magnetic Polarization ◽  
3 Dimensional ◽  
Equivalent Point ◽  
Gravity And Magnetic

A computational method, which combines the Gaussian quadrature formula for numerical integration and a cubic spline for interpolation in evaluating the limits of integration, is employed to compute directly the gravity and magnetic anomalies caused by 2-dimensional and 3-dimensional bodies of arbitrary shape and arbitrary magnetic polarization. The mathematics involved in this method is indeed old and well known. Furthermore, the physical concept of the Gaussian quadrature integration leads us back to the old concept of equivalent point masses or equivalent magnetic point dipoles: namely, the gravity or magnetic anomaly due to a body can be evaluated simply by a number of equivalent points which are distributed in the “Gaussian way” within the body. As an illustration, explicit formulas are given for dikes and prisms using 2 × 2 and 2 × 2 × 2 point Gaussian quadrature formulas. The basic limitation in the equivalent‐point method is that the distance between the point of observation and the equivalent points must be larger than the distance between the equivalent points within the body. By using a reasonable number of equivalent points or dividing the body into a number of smaller subbodies, the method might provide a useful alternative for computing in gravity and magnetic methods. The use of a simplified cubic spline enables us to compute the gravity and magnetic anomalies due to bodies of arbitrary shape and arbitrary magnetic polarization with ease and a certain degree of accuracy. This method also appears to be quite attractive for terrain corrections in gravity and possibly in magnetic surveys.

REMANENT MAGNETIZATION FROM COMPARISON OF GRAVITY AND MAGNETIC ANOMALIES

Geophysics ◽  
1976 ◽  
Vol 41 (1) ◽  
pp. 56-61 ◽  
Author(s):  
D. H. Shurbet ◽  
G. R. Keller ◽  
J. P. Friess
Keyword(s):  
Remanent Magnetization ◽  
Spatial Relationship ◽  
Gravity Anomalies ◽  
Magnetic Anomalies ◽  
The Body ◽  
Gravity And Magnetic

Gravity and magnetic anomalies caused by deeply buried rock bodies in northwest Texas are compared. Interpretation of the gravity anomalies by modeling is used to locate and define the geometry of the body in a way analogous to the use of bathymetry in studies concerned with magnetization of seamounts. The direction of magnetization is then determined from the spatial relationship between the gravity and magnetic anomalies. This procedure amounts to an in‐situ determination of direction of magnetization of the body. In one example direction of magnetization indicates the time of intrusion and in another it indicates regional heating since intrusion.

scholarly journals Inversion Technique of Physical Parameters Based on Regularization Extension Depth Constraint

2019 ◽  
Vol 23 (4) ◽  
pp. 331-338
Author(s):  
Yang Wang ◽  
Jun Li ◽  
Xuben Wang ◽  
Xingxiang Jian
Keyword(s):  
Physical Property ◽  
Magnetic Anomalies ◽  
Downward Continuation ◽  
Resolving Power ◽  
Depth Of Field ◽  
Inversion Method ◽  
Physical Parameters ◽  
Field Source ◽  
Gravity And Magnetic ◽  
Downward Continuation Of Gravity

Through the regularization downward continuation of gravity and magnetic anomalies, the depth of the field source can be solved. However, due to the Gibbs effect, the horizontal resolving power of the field source is poor. In view of this, based on the depth of field source established by regularization downward continuation, this paper proposes a physical property parameter inversion method based on iterative continuation and anomaly separation, which can effectively improve the inversion accuracy of superimposed anomaly physical parameters, and provide a new idea for solving the physical parameters of superposition gravity and magnetic anomalies.

COMBINED ANALYSIS OF GRAVITY AND MAGNETIC ANOMALIES

Geophysics ◽  
1951 ◽  
Vol 16 (1) ◽  
pp. 51-62 ◽  
Author(s):  
G. D. Garland
Keyword(s):  
Magnetic Anomalies ◽  
The Body ◽  
Rock Material ◽  
Combined Analysis ◽  
Gravity And Magnetic ◽  
Anomalous Density ◽  
The Relationship

The relationship betwen gravity and magnetic anomalies is investigated. It is shown that the ratio of the anomalous susceptibility to the anomalous density of an unknown body may be determined from gravimeter and vertical magnetometer observations, independent of assumptions as to the depth or form of the body. The use of this ratio in identifying the rock material of the body is discussed, and illustrated by applying the method to a well‐known case.

SPECTRAL ANALYSIS OF GRAVITY AND MAGNETIC ANOMALIES DUE TO RECTANGULAR PRISMATIC BODIES

Geophysics ◽  
1977 ◽  
Vol 42 (1) ◽  
pp. 41-50 ◽  
Author(s):  
B. K. Bhattacharyya ◽  
Lei‐Kuang Leu
Keyword(s):  
Spectral Analysis ◽  
Approximation Method ◽  
Magnetic Anomalies ◽  
The Body ◽  
Exponential Approximation ◽  
Prismatic Body ◽  
First Order ◽  
Gravity And Magnetic ◽  
Sums Of Exponentials ◽  
Prismatic Bodies

The spectra of gravity and magnetic anomalies due to a prismatic body can be expressed as sums of exponentials. The complex exponents of these exponentials are functions of frequency and locations of the corners of the body. An exponential approximation method is used for the analysis of the radial spectra of an anomaly and its first order moments for obtaining accurate estimates of the depths to the top and bottom of the body. A method has also been developed for determining approximately the location of the centroid of the body. When the location of the centroid and the depths to the top and bottom are known for the causative body, it is possible to calculate the horizontal dimensions with the help of the spectrum of the anomaly.

Transient Temperature Involving Oscillatory Heat Source With Application in Fretting Contact

2007 ◽  
Vol 129 (3) ◽  
pp. 517-527 ◽  
Author(s):  
Jun Wen ◽  
M. M. Khonsari
Keyword(s):  
Heat Source ◽  
Oscillation Amplitude ◽  
The Body ◽  
Transient Temperature ◽  
Dimensionless Frequency ◽  
Heat Sources ◽  
Infinite Body ◽  
Fitting Method ◽  
Wide Range ◽  
Analytical Expressions

An analytical approach for treating problems involving oscillatory heat source is presented. The transient temperature profile involving circular, rectangular, and parabolic heat sources undergoing oscillatory motion on a semi-infinite body is determined by integrating the instantaneous solution for a point heat source throughout the area where the heat source acts with an assumption that the body takes all the heat. An efficient algorithm for solving the governing equations is developed. The results of a series simulations are presented, covering a wide range of operating parameters including a new dimensionless frequency ω¯=ωl2∕4α and the dimensionless oscillation amplitude A¯=A∕l, whose product can be interpreted as the Peclet number involving oscillatory heat source, Pe=ω¯A¯. Application of the present method to fretting contact is presented. The predicted temperature is in good agreement with published literature. Furthermore, analytical expressions for predicting the maximum surface temperature for different heat sources are provided by a surface-fitting method based on an extensive number of simulations.

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