In a recent paper, Won discussed the application of Gauss's method for obtaining the parameters of a dipping dike from its magnetic anomaly. He assumed the magnetization to be entirely induced and did not consider the effect of the presence of any permanent magnetism. In view of the reported agreement of the calculated dip angles with drilled results, the assumption seems to be valid in this particular case. If permanent magnetization in an unknown direction is present, neither the dip angle of the dike nor the susceptibility can be determined, although the other parameters of the dike (i.e., depth to the top, horizontal location, and thickness) can be deduced from the magnetic anomaly. The dip angle of the dike and the angle made by the transverse component of the resultant intensity of magnetization combine to form a single angle which alone can be determined uniquely from the magnetic anomaly. If the transverse component of the resultant intensity of magnetization is J and it dips at an angle a below the horizontal, then using the other notations given by Won it can be shown that
ΔZ=2Jsinξ2[cos(α+ξ2)(ϕ1ϕ2)]+sin(α+ξ2)in(r2/r1)],
and
ΔH=2Jsinξ2[sin(α+ξ2)(ϕ1ϕ2)]cos(α+ξ2)in(r2/r1)],
(Bruckshaw and Kunaratnam, 1963). For this reason, the magnetic anomaly due to an inclined dike of infinite depth extent and horizontal top surface is the same as that due to a vertical dike having the same top surface but for a modified direction and intensity of magnetization. The inclined dike anomalies can, therefore, be analyzed using the vertical prism models as well. If the magnetization is entirely induced, the dip angle of the inclined dike can be deduced from the direction of magnetization of the equivalent vertical dike.
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