Comparative investigations about the applicability of current density pseudosections in the interpretation of 2D VLF vertical magnetic anomalies

Takács, E. and Pethő, G. and Szabó, I. (2005) Comparative investigations about the applicability of current density pseudosections in the interpretation of 2D VLF vertical magnetic anomalies. Acta Geodaetica et Geophysica Hungarica, 40 (2). pp. 127-146. ISSN 1217-8977

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Abstract

Current density pseudosections derived by filtering and probability tomography from calculated VLF vertical magnetic profiles over synthetic 2D targets with geometrical shape are examined critically. It was found that the position and shape of  target only in the case of single inhomogeneities with very limited cross-sectional area and simple shape can be revealed reliably by them. The locations of sharp cross-sectional boundaries can only be guessed. Fictitious, misleading current-density indications occur in the case of laterally extended, or multiple targets at too wide filter windows. Both procedures suppose that the measured values originate in the superposition of the magnetic fields of individual stationary current-lines inside the target. It is shown that in the quasistationary range the shape and position of the target can be outlined sharply using this simplified form of the forward problem solution and performing an inversion with respect of the vertices of the polygon approximating the cross-sectional contour of the target. Several kinds of inversionprocedures  were tested.

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