Exploration Geophysics - Volume 9, Issue 2, 1978

When the horizontal and vertical gradients of either the magnetic or gravity fields are plotted against each other, some interesting graphs may result. In the case of the geological contact the symmetry and characteristic points of the loci can be directly related to the parameters defining the structure. The vertical gradient may be calculated from the more readily measured horizontal one by applying a Hilbert Transform. When the two derivatives of gravity over a contact are plotted against each other the graph closely resembles an ellipse. The loci of the magnetic gradients over this same body is precisely circular. In both cases the method is given for relating the characteristic points of these loci to the parameters defining the structure.

The modelling arrangement, instrumentation and experimental procedure for simulating the vertical magnetic field component response of the rotating current dipole E.M. method are described. Scaling considerations appropriate to the Australian subsurface environment are discussed and preliminary examples given of the phase and ratio response of a graphitic model in an electrolytic tank. These examples are presented as evidence of the method's ability to optimize anomalies.