Vertical seismic profiling of glaciers: appraising multi-phase mixing models
2013 (English)In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 54, no 64, 115-123 p.Article in journal (Refereed) Published
We have investigated the speed of compressional waves in a polythermal glacier by, first, predicting them from a simple three-phase (ice, air, water) model derived from a published ground-penetrating radar study, and then comparing them with field data from four orthogonally orientated walkaway vertical seismic profiles (VSPs) acquired in an 80 m deep borehole drilled in the ablation area of Storglaciaren, northern Sweden. The model predicts that the P-wave speed increases gradually with depth from 3700 m s(-1) at the surface to 3760 m s(-1) at 80 m depth, and this change is almost wholly caused by a reduction in air content from 3% at the surface to <0.5% at depth. Changes in P-wave speed due to water content variations are small (<10 m s(-1)); the model's seismic cold-temperate transition surface (CTS) is characterized by a 0.3% decrease downwards in P-wave speed (about ten times smaller than the radar CTS). This lack of sensitivity, and the small contrast at the CTS, makes seismically derived water content estimation very challenging. Nevertheless, for down-going direct-wave first arrivals for zero- and near-offset VSP shots, we find that the model-predicted travel times and field observations agree to within 0.2 ms, i.e. less than the observational uncertainties.
Place, publisher, year, edition, pages
2013. Vol. 54, no 64, 115-123 p.
Physical Geography Geosciences, Multidisciplinary
IdentifiersURN: urn:nbn:se:su:diva-95098DOI: 10.3189/2013AoG64A106ISI: 000324720300015OAI: oai:DiVA.org:su-95098DiVA: diva2:658542
Alaska Climate Science Center; United States Geological Survey G10AC00588; Jeremy Willson Charitable Trust; Consorzio del Comuni del Bacino Imbrifero Montano dell'Adda; Percy Sladen Fund Mount Everest Foundation; British Society for Geomorphology; Quaternary Research Association; Dudley Stamp Memorial Fund; Earth and Space Foundation; Swedish Research Council 621-2007-3752B .2013-10-222013-10-212013-10-22Bibliographically approved