Nomogram for the direct interpretation of magnetic anomalies due to long horizontal cylinders

Abstract

One of the widely used geometrical configurations for magnetic interpretation is the long horizontal circular cylinder. Gay (1965) provides a set of master curves for the interpretation of magnetic anomalies of these bodies. Rao et al. (1973) formulates functions of the anomaly at several distances from an arbitrary point, and the linear equations thus formed are solved for coefficients related to the parameters of the causative body. Prakasa Rao and Murthy (1976) propose an empirical method for rapid interpretation. Atchuta Rao and Ram Babu (1980), Mohan et al. (1982), and Sampath Kumar and Prakasa Rao (1984) describe methods based on Hilbert transforms. Radhakrishna Murthy et al. (1980) propose a method based on two components of the anomalous magnetic field. With the exception of the direct method of Prakasa Rao and Murthy (1976), the other methods mentioned involve reduction of field curves and then matching with master curves, solving linear equations, performing Hilbert transformations, and computation of derivatives, respectively. Hence they are not suitable for direct and rapid interpretation. This note contains a simple nomogram for the magnetic effect due to an arbitrarily magnetized horizontal cylinder.

Inversion of Source Parameters from Magnetic Anomalies for Mineral/Ore Deposits Exploration Using Global Optimization Technique and Analysis of Uncertainty

“…Gay (1963Gay ( , 1965 and McGrath (1970) have developed the curve matching techniques. Other elucidation methods that were developed include Fourier transform techniques, Hilbert transforms, monograms, characteristic points and distance approaches, least-squares residual anomalies (Bhattacharyya 1965;Grant and West 1965;Mohan et al 1982;Prakasa Rao et al 1986;Abdelrahman 1994;Abdelrahman and Sharafeldin 1996). Many linear and linearized inversions such as least squares, linearized least squares, normalized local wave number method, analytic signal derivatives, second-horizontal derivatives, Euler deconvolution method, simplex algorithm, fair function minimization have also been developed (McGrath and Hood 1973;Silva 1989;Salem and Ravat 2003;Salem et al 2004;Salem 2005;Salem and Smith 2005;Tlas and Asfahani 2011a, b;Abdelrahman and Essa 2015;Tlas and Asfahani 2015).…”

A very fast simulated annealing method for inversion of magnetic anomaly over semi-infinite vertical rod-type structure

“…Analyses of magnetic data are generally performed with the help of different interpretation techniques. The interpretation methods include curves matching (Gay 1963(Gay , 1965McGrath 1970), Fourier transform (Bhattacharyya 1965), Hilbert transforms (Mohan et al 1982), monograms (Prakasa Rao et al 1986), least squares minimization (McGrath and Hood 1973;Silva 1989), characteristic points and distance approaches (Grant and West 1965;Abdelrahman 1994), correlation factors between successive least-squares residual anomalies (Abdelrahman and Sharafeldin 1996), Henkel transform (Singh et al 2000), linearized least squares (Salem et al 2004), normalized local wave number (Salem and Smith 2005), analytic signal derivatives (Salem 2005), Euler deconvolution (Salem and Ravat 2003), Fair function minimization (Tlas and Asfahani 2011a), deconvolution technique (Tlas and Asfahani 2011b), secondhorizontal derivatives (Abdelrahman and Essa 2015), Simplex algorithm (Tlas and Asfahani 2015). Also, simulated annealing (Gokturkler and Balkaya 2012), very fast simulated annealing (Sharma and Biswas 2013a;Sharma 2014a, b, 2015;Biswas 2015), Particle swarm optimization (Singh and Biswas 2016) have been effectively used to solve similar nonlinear inversion problems of geometrically simple bodies.…”

An Iterative Approach to Depth Determination from Second Moving Average Residual Magnetic Anomalies

“…Parameters K and θ define the components of the magnetic anomaly being measured (Gay, 1963 and1965;Prakasa Rao et al, 1986;and Prakasa Rao and Subrahmanyan, 1988). Examples of K and θ for the vertical (∆V), horizontal (∆H) and total-field (∆T) anomalies for the case of thin dikes and horizontal cylinders are given in Table 2.…”

“…The models may not be geologically realistic, but useful approximate equivalence is sufficient to determine whether the form and magnitude of calculated magnetic effects are close enough to the observed magnetic data to make the geological postulate reasonable. However, very often the existence of interfering sources is a problem to use of quantitative methods of evaluation such as those given by Werner (1953), Gay (1963Gay ( , 1965, Grant and West (1965), Hartman et al (1971), Rao et al (1973), Jain (1976), Stanley (1977), Atchuta Rao and Ram Babu (1980), Mohan et al (1982), Thompson (1982), Prakasa Rao et al (1986), Prakasa and Subrahmanyan (1988) and many others. It is, in circumstance such as these, that the interpretation of magnetic data must involve initial steps to remove unwanted field components in order to isolate the desired anomaly (e.g.…”