The approximation of buried simple conductive three - dimensional (3 - D) inhomogeneities by two # dimensional (2 - D) inhomogeneities is investigated numerically using the Rayleigh-FfT modeling technique. The technique is applicable to curved interfaces between regions of different conductivity. The effects of the increased aspect ratio of the 3 - D models on the apparent resistivities, skew and tipper for the E - parallel and E - perpendicular modes are studied. Also investigated is the behaviour of these quantities when the condition for electrodynamio similitude to exist between two models is satisfied. The results show that 3 - D E - perpendicular mode apparent resistivities and the 2 - D Transverse magnetic (TM) mode, values agree very closely. The 3 - D E - parallel mode apparent resistivities are sensitive to strike extent and frequency and approach the ? - D Transverse eleotric (TE) mode results as the aspect ratio is increased. It is found that the ratio of the width of the inhomogeneity to the skin depth in the half-space is a very important quantity in predicting the percentage difference between the 2 - D and 3 - D values at a given aspect ratio. Very simple guidelines for the above prediction are given for models having conductivity contrast of 1 : 10 or its powers. The maximum skew values for the 3 - D models decreased by about 60 percent for a change in aspect ratio from 2 to 4 and ..m remained constant when the aspect ratio is changed from 4 to 6. In general, as the aspect ratio is increased the tipper azimuths around the. middle of the inhomogeneities indicated the long axes of the bodies. When the condition for similitude to exist between two models is satisfied, it is found that the apparent resistivities are appropriately scaled while the skew values, tipper magnitudes and tipper azimuths are the same for both models. |