Inversion and interpretation of two-dimensional geoelectrical measurements for detecting permafrost in mountainous regions

The use of tomographic geoelectrical measurements for the detection of ground ice occurrences in mountainous regions is evaluated. Because isolated ground ice occurrences in a warming climate may be subject to rapid thawing, they present a future hazard in the context of thawing-permafrost-induced landslides and rockfalls. Isolated permafrost occurrences are difficult to detect with commonly used one-dimensional sounding techniques, as plane-layer approximations for the inversion are often invalid. Therefore, recently developed two-dimensional tomographic inversion schemes are used to yield realistic near-surface geological models. The method is applied to various types of permafrost occurrences in the European Alps. The influence of topography, measurement geometry and different inversion parameters are discussed. In addition, complimentary seismic survey results are used to exclude the possibility of air-filled cavities, which exhibit similarly high resistivities as ground ice occurrences. The results show a large variety of influencing parameters which have to be considered in resistivity inversion and interpretation. Copyright (C) 2003 John Wiley Sons, Ltd.