A METHOD FOR COMPUTING THE TOTAL MAGNETIZATION VECTOR AND THE DIMENSIONS OF A RECTANGULAR BLOCK‐SHAPED BODY FROM MAGNETIC ANOMALIES

Abstract

In this paper is presented a new method for determining the following parameters of a uniformly magnetized body of rectangular prismatic shape: (i) horizontal dimensions, (ii) depths to the top and bottom of the body, and (iii) intensity and direction of magnetization. Accuracy in the computation of these parameters is highly dependent on the correct location of the center and on the determination of the major and minor axes of the body. An iterative method of calculations is used. This method is considerably aided not only by the second vertical derivative map of the observed total field but also by the total field reduced to the pole and its second vertical derivative map. The horizontal dimensions are determined by noting the location of the maximum of the odd component of the second vertical derivative about the center of the body. These dimensions are estimated with high accuracy when they are greater than the depth to the top of the body. The remaining unknown parameters of the body are calculated with the help of the first horizontal and vertical derivatives and the total field at the origin in the plane of observation which is directly above the center of the body. The present method also requires the total‐field value at the point one‐half unit of length above the origin. The factors affecting the accuracy in the calculation of the parameters are discussed in detail. With the help of high‐speed digital computers, this method can be used with great advantage for computation of the above parameters of magnetized bodies giving rise to a number of anomalies over a particular area.