Publication Date:
2019-07-17
Description:
Explosive seismic reflection data from Halvfarryggen, a 910m thick local ice dome of the
Antarctic ice sheet, show numerous laterally continuous reflections within the ice between 300 and
870m 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, 40m 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.
Repository Name:
EPIC Alfred Wegener Institut
Type:
Article
,
isiRev
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