GRAPHICAL CALCULATION OF TOTAL‐INTENSITY ANOMALIES OF THREE‐DIMENSIONAL BODIES

Abstract

Calculation of the total‐intensity anomaly of a three‐dimensional body of arbitrary shape is greatly facilitated by the orthographic projection of a topographic map of the body onto a plane normal to the inducing field. The graphical integration is then effected by a modified Gassmann integration process. Applications to theoretical and laboratory models establish the relative accuracy of the method. Examples are given of applications to observed anomalies over two laccoliths, Round Butte and Square Butte, in Montana.