Open AccessMacro‐anisotropy of the electrical conductivity of the crust: a magnetotelluric study of the German Continental Deep Drilling site (KTB)
Author(s) -
Eisel Markus,
Haak Volker
Publication year - 1999
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1046/j.1365-246x.1999.00707.x
Subject(s) - magnetotellurics , geology , crust , anisotropy , geophysics , tectonics , continental crust , seismology , drilling , petrology , electrical resistivity and conductivity , mechanical engineering , physics , quantum mechanics , electrical engineering , engineering
Summary The interpretation of magnetotelluric (MT) data collected in the vicinity of the German Continental Drilling Project (KTB) has revealed two major structures in the Earth’s crust. First, a large‐scale mid‐crustal layer of enhanced conductivity is required to fit the regional observations of the anomalous vertical magnetic field. Second, the MT impedances of the area close to the KTB, namely the crustal unit of the Zone Erbendorf‐Vohenstrauß (ZEV), support a model with a highly anisotropic upper to middle crust. The extremely high values of anisotropy derived from the MT measurements exceed the values of anisotropy observed on rock samples in the laboratory by an order of magnitude and therefore exclude intrinsic features as a source for the observed anisotropy. The regional mid‐crustal conductor is in agreement with Central Europe‐wide observations of high‐conductivity layers in the crust, while the proposed model of well‐conducting, subvertical dykes within a resistive host rock explains the MT observations and agrees with the steeply dipping seismic reflectors, the downhole and core observations from the drilling and the model of the tectonic development of this area. However, the superposition of both structures leaves some unanswered questions.