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  • 1
    Call number: ZSP-201-79/23
    In: CRREL Report, 79-23
    Description / Table of Contents: The performance of surface impedance and magnetic induction electromagnetic subsurface exploration techniques was studied seasonally at various sites in Alaska where permafrost and massive ground ice occurred. The surface impedance method, which uses radiowaves in the LF and VLF bands, and the magnetic induction method, which uses low-frequency magnetic induction fields, distinguish subsurface materials by the electrical resistivity of the materials. The methods used have greatest sensitivity within about 20 m of the surface and are, therefore, most applicable for shallow subsurface investigations. The selection of study sites was based on anticipated contrasts in electrical resistivity between ground ice and adjacent earth materials. A magnetic induction instrument, using a separation of 3.66-m between the transmitter and receiver antennas, in general was able to detect near-surface zones of massive ice and to provide data regarding permafrost distribution in both the Fairbanks and Prudhoe Bay areas. At this antenna separation, the depth of magnetic field penetration was sufficient to include mainly the zone containing maximum contrasts in resistivity between ground ice and other earth materials. In the Fairbanks area, contrasts, in this zone were greatest in late winter when the seasonally thawed surface layer was completely frozen. When thawed, this layer usually becomes more conductive and often masks the deeper resistivity contrasts. In the Prudhoe Bay area, maximum ground resistivity contrasts were detected in late summer when shallow subsurface temperatures had risen sufficiently to permit resistivity contrasts between the massive ice and the ice-rich ground to appear.
    Type of Medium: Series available for loan
    Pages: v, 24 Seiten , Illustrationen
    Series Statement: CRREL Report 79-23
    Language: English
    Note: CONTENTS Abstract Preface Introduction Background Obiectives and procedures Ground electrical resistivity in permafrost regions Electromagnetic techniques General Magnetic induction method Surface impedance fradiowave method Direct current method General description of field sites Results Site 1 CRREL permafrost station, Fairbanks, Alaska Site 2 Planned road cut for Steese Highway near Fox, Alaska Site 3 Relic floodplain near Fairbanks, Alaska Site 4 Pingos, Prudhoe Bay, Alaska Site 5 Ice wedges, Prudhoe Bay, Alaska Comparisons between the surface impedance and magnetic induction methods Conclusions and recommendations Literature cited Appendix A. Discussion of the depth of sensitivity of the magnetic induction method using two- and three-layer apparent resistivity curves
    Location: AWI Archive
    Branch Library: AWI Library
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