The Cryosphere www.the-cryosphere.net 1994-0416 1994-0424 4 3 2010 10.5194/tc-4-243-2010 http://www.the-cryosphere.net/4/243/2010/ http://www.the-cryosphere.net/4/243/2010/tc-4-243-2010.html http://www.the-cryosphere.net/4/243/2010/tc-4-243-2010.pdf 243 259 2010-07-16 Time-lapse refraction seismic tomography for the detection of ground ice degradation C. Hilbich chilbich@geo.uzh.ch Institute for Geography, University of Jena, Germany Institute for Geography, University of Zurich, Switzerland The ice content of the subsurface is a major factor controlling the natural hazard potential of permafrost degradation in alpine terrain. Monitoring of changes in ice content is therefore similarly important as temperature monitoring in mountain permafrost. Although electrical resistivity tomography monitoring (ERTM) proved to be a valuable tool for the observation of ice degradation, results are often ambiguous or contaminated by inversion artefacts. In theory, the sensitivity of P-wave velocity of seismic waves to phase changes between unfrozen water and ice is similar to the sensitivity of electric resistivity. Provided that the general conditions (lithology, stratigraphy, state of weathering, pore space) remain unchanged over the observation period, temporal changes in the observed travel times of repeated seismic measurements should indicate changes in the ice and water content within the pores and fractures of the subsurface material. In this paper, a time-lapse refraction seismic tomography (TLST) approach is applied as an independent method to ERTM at two test sites in the Swiss Alps. 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