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dc.contributor.authorZechman, Jenna M.
dc.date.accessioned2017-06-14T01:26:46Z
dc.date.available2017-06-14T01:26:46Z
dc.date.issued2017-05
dc.identifier.urihttp://hdl.handle.net/11122/7654
dc.descriptionThesis (M.S.) University of Alaska Fairbanks, 2017en_US
dc.description.abstractSubglacial materials play an important role in glacier dynamics. High pore-pressure, high porosity (dilatant) tills can contribute to high basal motion rates by deforming. Amplitude Variation with Angle (AVA) analysis of seismic reflection data uses the relationship between basal reflectivity and reflection incidence angle to characterize the subglacial material. This technique can distinguish between dilatant tills and less-porous, non-deforming (dewatered) tills due to their distinctive reflectivity curves. However, noise from crevasses and glacier geometry effects can complicate reflectivity calculations, which require a source amplitude derived from the bed reflection multiple. We use a forward model to produce synthetic seismic records, including datasets with and without visible bed reflection multiples. The synthetic data are used to test source amplitude inversion and crossing angle analysis, which are amplitude analysis techniques that do not require absolute reflectivity calculations. We and that these alternative methods can distinguish subglacial till types, as long as reflections from crevasses do not obscure the bed reflection. The forward model can be used as a planning tool for seismic surveys on glaciers, as it can predict AVA success or failure based on crevasse geometries from remote sensing data and glacier bed geometry from radar or from a worst-case-scenario assumption of glacier bed shape. Applying lessons from the forward model, we perform AVA on a seismic dataset collected from Taku Glacier in Southeast Alaska in March 2016. Taku Glacier is a valley glacier thought to overlay thick sediment deposits. It has been the subject of numerous studies focusing on its ice-sediment interactions. Our analysis indicates that Taku Glacier overlies unconsolidated tills with porosity values greater than 33 %, though because of uncertainties due to the lack of a bed reflection multiple, it is possible that the tills are not dilatant.en_US
dc.language.isoen_USen_US
dc.subjectGlaciersen_US
dc.subjectAlaskaen_US
dc.subjectTaku Glacieren_US
dc.subjectDynamicsen_US
dc.subjectAmplitude variation with offset analysisen_US
dc.titleStrategies for applying active seismic subglacial till characterization methods to valley glaciersen_US
dc.typeThesisen_US
dc.type.degreemsen_US
dc.identifier.departmentDepartment of Geosciencesen_US
dc.contributor.chairTruffer, Martin
dc.contributor.chairLarsen, Christopher F.
dc.contributor.committeeCoakley, Bernard J.
dc.contributor.committeeAmundson, Jason M.
refterms.dateFOA2020-03-05T14:29:36Z


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