Open Access2‐D or 3‐D interpretation of conductivity anomalies: example of the Rhine‐Graben conductivity anomaly
Author(s) -
Menvielle M.,
Tarits P.
Publication year - 1986
Publication title -
geophysical journal of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0016-8009
DOI - 10.1111/j.1365-246x.1986.tb04354.x
Subject(s) - graben , geology , anomaly (physics) , geophysics , massif , magnetic anomaly , conductivity , dynamo , sedimentary basin , seismology , geomorphology , structural basin , magnetic field , physics , condensed matter physics , paleontology , quantum mechanics
Summary. Evidence of a conductivity anomaly in the Rhine‐Graben was first given about 15 years ago and consequently led to the definition of various models of induction in the region for periods ranging from a few minutes to a few hours. These models reflect two antagonistic ways of explaining the observed anomalous variations of the magnetic field: direct induction in a two‐dimensional (2‐D) structure or static distortion of telluric currents by the resistive crystalline Vosges (France) and Schwarzwalde (Germany) massifs. We discuss the two approaches using a simple formalism. In particular, we show that the self‐induction related to the anomalous currents flowing in the Rhine‐Graben is negligible for periods larger than 1000 s, and that, even though the static distortion of telluric currents does account for the observed anomaly, 2‐D models can explain some of its features. We also show how the channelled currents are induced in the large sedimentary basins surrounding the area under study. An experimental verification of this result is given.