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| Titel |
Time-lapse refraction seismic tomography for the detection of ground ice degradation |
| VerfasserIn |
C. Hilbich |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1994-0416
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| Digitales Dokument |
URL |
| Erschienen |
In: The Cryosphere ; 4, no. 3 ; Nr. 4, no. 3 (2010-07-16), S.243-259 |
| Datensatznummer |
250001761
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| Publikation (Nr.) |
 copernicus.org/tc-4-243-2010.pdf |
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| Zusammenfassung |
| 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. The approach was tested and validated based on a) the
comparison of time-lapse seismograms and analysis of reproducibility of the
seismic signal, b) the analysis of time-lapse travel time curves with
respect to shifts in travel times and changes in P-wave velocities, and c) the comparison of inverted tomograms including the quantification of
velocity changes. Results show a high potential of the TLST approach
concerning the detection of altered subsurface conditions caused by freezing
and thawing processes. For velocity changes on the order of 3000 m/s even an
unambiguous identification of significant ice loss is possible. |
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