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Subglacial sediment distribution from constrained seismic inversion, using MuLTI software: examples from Midtdalsbreen, Norway
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Number of Authors: 62019 (English)In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 60, no 79, p. 206-219Article in journal (Refereed) Published
Abstract [en]

Fast ice flow is associated with the deformation of subglacial sediment. Seismic shear velocities, Vs, increase with the rigidity of material and hence can be used to distinguish soft sediment from hard bedrock substrates. Depth profiles of Vs can be obtained from inversions of Rayleigh wave dispersion curves, from passive or active-sources, but these can be highly ambiguous and lack depth sensitivity. Our novel Bayesian transdimensional algorithm, MuLTI, circumvents these issues by adding independent depth constraints to the inversion, also allowing comprehensive uncertainty analysis. We apply MuLTI to the inversion of a Rayleigh wave dataset, acquired using active-source (Multichannel Analysis of Surface Waves) techniques, to characterise sediment distribution beneath the frontal margin of Midtdalsbreen, an outlet of Norway's Hardangerjokulen ice cap. Ice thickness (0-20 m) is constrained using co-located GPR data. Outputs from MuLTI suggest that partly-frozen sediment (Vs 500-1000 m s(-1)), overlying bedrock (Vs 2000-2500 m s(-1)), is present in patches with a thickness of similar to 4 m, although this approaches the resolvable limit of our Rayleigh wave frequencies (14-100 Hz). Uncertainties immediately beneath the glacier bed are <280 m s(-1), implying that MuLTI cannot only distinguish bedrock and sediment substrates but does so with an accuracy sufficient for resolving variations in sediment properties.

Place, publisher, year, edition, pages
2019. Vol. 60, no 79, p. 206-219
Keywords [en]
glacier geophysics, seismology, subglacial exploration geophysics, subglacial sediments
National Category
Earth and Related Environmental Sciences
Identifiers
URN: urn:nbn:se:su:diva-173098DOI: 10.1017/aog.2019.13ISI: 000480289300017OAI: oai:DiVA.org:su-173098DiVA, id: diva2:1357986
Available from: 2019-10-05 Created: 2019-10-05 Last updated: 2019-10-05Bibliographically approved

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Reinardy, Benedict T.
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Department of Physical Geography
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CiteExportLink to record
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  • apa
  • ieee
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  • nn-NO
  • nn-NB
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  • asciidoc
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