CGRG Bibliography of Canadian Geomorphology
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Author : Fortier, R.; and LeBlanc, A.-M.
Date : 2004.
Title : 2D inversion of IP profiling for geocryologic study of permafrost mounds in Nunavik, Canada.
Publication : European Geosciences Union. 1st General Assembly. Nice, France, 25 - 30 April 2004.
Issue : EGU04-A-00932.
Page(s) :
Abstract
During the summer of 1998, a induced polarization (IP) profiling has been carried out to study the spatial distribution of ground ice in two permafrost mounds in the "Vallée des Trois" near the Inuit community of Umiujaq in Nunavik, Québec, Canada. Pseudosections of electrical resistivity and chargeability are currently used as the standard form of data presentation of IP profiling. However, pseudo-sections give a misrepresented cross-section of the environment due to the electrodes array used in the field. To avoid this problem, inversion of IP profiling has been performed using DCIP2D developed by BGC-GIF to create realistic models of underground cross-section. Estimating the spatial distribution of subsurface electrical properties based on IP data is well known as the solution of the inverse problem. The purpose of the present study is to create the most representative and realistic electrical resistivity and chargeability models of the frozen ground. The inverse models show clearly the presence of ice-rich core in the permafrost mounds. The ice-rich cores are underlined by high resistivity values while the unfrozen zones show low resistivity values. The localisation of the permafrost table is highlighted by a strong contrast of resistivity while the permafrost base is marked by an abrupt change of resistivity and chargeability values. In the hollow between the permafrost mounds, the models show low resistivity values characteristic of a talik zone. A synthetic resistivity sounding built from the most acceptable inverse model correlates very well with an electrical resistivity logging carried out in one permafrost mound at the same period. In conclusion, the inversion of IP profiling must be done for defining realistic model of study site. IP profiling can be used for the delineation of ice-rich zones and taliks in frozen ground along major transect such as the construction of pipelines and roads in permafrost environment.
Bibliography of Canadian Geomorphology