A Parametric Study of the Magnetometric Resistivity Response of a Dipping Dyke

Nick Bartzis - Bachelor of Science (Honours)

This thesis aims to simplify the interpretation of the magnetometric resistivity (MMR) response for a dipping dyke. This is conducted by evaluating the effect of each of the parameters associated with the dyke model on the horizontal and vertical component MMR anomalies. Of particular interest is the change in ability to resolve the dip and depth of a dyke with different strike lengths, depth extents and thicknesses of conductive overburden.

An evaluation of the parameters found that the dip, depth of burial, strike length, conductivity contrast and the introduction of a conductive overburden significantly affects the shape and amplitude of the resulting MMR profiles. Compared to changes in width and depth extent, where only minor differences exist, this behaviour is related to current saturation.

The range of characteristic curves developed here show that the ability to determine dip and depth is possible for a large range of realistic dykes. As the strike length increases the ability to resolve dip and depth increases. Also, changes in the depth extent and the introduction of a conductive overburden significantly alter the shape of the characteristic curves.

Finally it was found that the 2D gravity analogy for MMR interpretation provides a poor representation of the response due to a 3D dyke with a large electrode spacing and/or a large strike length. However some intuitive idea of the orientation of the dyke can be gained by this technique. Compared to the MMR response for a approximate model of a dipping dyke developed by Edwards (1983) which successfully estimates the amplitude and shape of the response from a 3D MMR finite difference program for similar dykes at shallow depths and, is only a constant factor less when approximating dykes at greater depths. This constant factor increases with depth of burial.



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