Magneto-Telluric Experiments in Northern Ellesmere Island
During the 1963 field season, a magneto-telluric experiment was successfully undertaken at and near Alert, in northern Ellesmere Island. Analysis of the results shows that the electric field is very strongly confined to a direction nearly N–S, that a strongly inhomogeneous or anisotropic situation e...
| Published in: | Geophysical Journal International |
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| Main Authors: | , |
| Format: | Text |
| Language: | English |
| Published: |
Oxford University Press
1965
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| Subjects: | |
| Online Access: | http://gji.oxfordjournals.org/cgi/content/short/10/3/317 https://doi.org/10.1111/j.1365-246X.1965.tb03158.x |
| Summary: | During the 1963 field season, a magneto-telluric experiment was successfully undertaken at and near Alert, in northern Ellesmere Island. Analysis of the results shows that the electric field is very strongly confined to a direction nearly N–S, that a strongly inhomogeneous or anisotropic situation exists with the electric field in phase (±5°) with the horizontal magnetic field for periods between 240 and 6000 s, and that the electric to magnetic field ratio is constant and very small (0.12(6) mV km−1 γ−1) in the same period range. At Lake Hazen, 150km to the SW approximately, the experimental data is of poorer quality, but the inhomogeneity or anisotropy is weaker, the mean direction of the electric field between 20 and 30° E of N, the phase advance of the electric over the magnetic field nearly 45° and the electric to magnetic field ratio is frequency dependent. The magnetic variations measured at Lake Hazen suggest an extension along strike of the Alert anomaly. The Alert results are not consistent in inhomogeneity, phase and frequency dependence with earlier models used to explain the magnetic variation anomaly observed in northern Ellesmere Island. Equally an interpretation of the magneto-telluric results in terms of a near surface plane conductor with a very large height-integrated conductivity ≃6(.3) × 10−6 emu is not consistent with the earlier magnetic variation results, fails to explain the inhomogeneity or anistropy, and makes no geological or common sense. The inductive situation is very complex and it appears that boundary arguments must be very important and need theoretical elucidation. At the present time no self-consistent hypothesis can be derived : some of the problems in deducing one are demonstrated in the text using illustrative calculations. |
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