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Anisotropy in Flowing Firn and Ice: Insights from Ambient Noise and Active Source Studies in Antarctica

Description: 

Antarctic firn, which covers 99% of the Antarctic ice sheet, promotes a variety of exotic seismic behaviors owing to its porosity, extreme shallow velocity and density gradients, and highly dynamic and evolving nature. Ambient noise excitation of firn through wind forcing creates patterns of spectral amplifications that are sensitive to both static shallow structure and surface environmental forcing effects. Spectral peaks demonstrate pervasive offsets across seismic components, pointing to a sensitivity to azimuthal anisotropy as well. Here, we show that spectral peak offsets can be interpreted in the context of flowing ice and snow and can be systematically used to determine frequency-dependent anisotropy. We show example results from Ross Ice Shelf seismic arrays and preliminary nodal networks from the TIME project, validated by direct comparison to active source experiments. Flowing firn and ice demonstrate multiple kinds of anisotropy that vary with depth, with brittle fracture accommodation of stress dominating in solid ice and plastic foam-like extension in shallow firn. We also present preliminary results from recent large-N nodal arrays deployed in the TIME project during the 2022 and 2023 field seasons.

Session: Anisotropy Across Scales - I

Type: Oral

Date: 5/3/2024

Presentation Time: 08:45 AM (local time)

Presenting Author: Julien

Student Presenter: No

Invited Presentation: Yes

Authors