Details

Autor(en) / Beteiligte

• Hofstede, Coen
• Eisen, Olaf
• Diez, Anja
• Jansen, Daniela
• Kristoffersen, Yngve
• Lambrecht, Astrid
• Mayer, Christoph

Titel

Investigating englacial reflections with vibro- and explosive-seismic surveys at Halvfarryggen ice dome, Antarctica

Ist Teil von

• Annals of glaciology, 2013-01, Vol.54 (64), p.189-200

Ort / Verlag

Cambridge, UK: Cambridge University Press

Erscheinungsjahr

2013

Link zum Volltext

Quelle

Free E-Journal (出版社公開部分のみ）

Beschreibungen/Notizen

• Explosive seismic reflection data from Halvfarryggen, a 910 m thick local ice dome of the Antarctic ice sheet, show numerous laterally continuous reflections within the ice between 300 and 870 m depth. We compare the quality of data obtained with explosive sources with that obtained using a vibroseis source for detecting englacial reflections with a snowstreamer, and investigate the origin of englacial reflections. We find vibroseis in combination with a snowstreamer is ten times more productive than explosive seismics. However, englacial reflections are more clearly visible with explosives, which have a broader bandwidth signature, than the vibroseis, which is band-limited at the high-frequency end to 100 Hz. Only the strongest and deepest englacial reflection is detected with vibroseis. We interpret the majority of englacial reflections to originate from changes in the crystal orientation fabric in closely spaced layers, less than the vibro-seismic tuning thickness of 13.5 m. Phase analysis of the lowermost englacial reflector, 40 m above the bed, indicates a sharp increase in seismic wave speed. We interpret this reflector as a transition to a vertical single-maximum fabric. Our findings support current results from anisotropic ice-flow models, that crystal fabric is highly anisotropic at ice domes, both laterally and vertically.