Relation of the graphite and fluid bearing conducting dikes to the tectonics and seismicity (review on the Transdanubian crustal conductivity anomaly)

Two Hungarian geophysical institutes (GGRI, ELGI) carried out about 300 mag netotelluric (MT) deep soundings in the NW part of Transdanubia (W-Hungary) partly along basic profiles, partly in areal distribution. These measureme nts aimed first of all at the determination of the tectonic structures repr esented by a strong conductivity anomaly (CA) detected in the early 1960's in the upper crust. The analysis of the conductivity anomaly has been made by successive approximation i.e. by pseudosections, 1D inversion and 2D inv ersion. For the 2D inversion the regional strike direction has been determi ned by the rose diagram of the Groom-Bailey decomposition strikes, by elect romagnetic (EM) distortion analysis and by "phase maps" and found that the regional strike-direction is NE-SW. Using different 2D inversion techniques , the tectonic structure of the presumably Paleozoic graphite and fluid con taining conductors representing almost parallel strike slips, shear zones a nd the thrust sheets, etc. have been determined. The low viscosity graphite and/or fluid could be smeared into the tectonic zones as it appears in the highly conducting dikes which can influence the stress accumulation of tec tonic earthquakes and can provide higher attenuation of the seismic waves.