Natural electromagnetism in the Rhine Graben

Summary. Together with experiments by differential geomagnetic soundings, magnetotelluric soundings have been performed in the Rhine Graben. The results of the former have been presented and discussed before. We try to show that it is not necessary to call upon the notion of induction in surrounding areas to justify the characteristics of the observed anomalous magnetic fields. Theoretical calculations of these fields on structures defined by the interpretation of magnetotelluric sounds, or by geological and other geophysical data, agree very well with experimental data. We conclude that magnetotelluric experiments and interpretations are valid as the Rhine Graben is a well-known region allowing us to verify our interpretation.