P. Schmoldt, PhD - MTNet - DIAS

9.8. Analysis of vertical magnetic transfer function data
Fig. 9.15.: Real induction vectors (Parkinson convention) for the Tajo Basin subsurface denoted by red arrows; the arrows are plotted
for a projection with North located to the top and East located to the right of this figure. The dashed blue lines indicates an area of
magnitude greater one (cf. Fig. 9.14), see text for further details.
profile (Fig. 9.15). Since real induction vectors are orthogonal to electric resistivity interfaces,
presuming no prevailing disturbance, this relates to a geoelectric strike direction
between N100W and N130W. This direction is similar to the results of the strike analysis
for the crustal region using the MT impedance tensor (cf. Sec. 9.6.1). Deviations from
these directions are observed particularly for a) data in the area of disturbance, discussed
in the previous paragraph, for b) longest-period data of most stations, and for c) shorter
period data of the southernmost station (pic019). Anomalies a and b are probably caused
by low signal-to-noise ratio, wherein the long-period deviation (b) could be due to low
resolution and related disturbance of the data by small amount of noise. The deviation
in the area of exceedingly high magnitude (a) most likely originates from disturbances
generated by the nearby DC railway line. The deviation at station pic019 (c) is probably
related to a conductive region to the west; inversion of the MT data should provide further
information about this feature.
223