Ambient high-frequency seismic surface waves in the firn column of central west Antarctica

Firn is the pervasive surface material across Antarctica, and its structures reflect its formation and history in response to environmental perturbations. In addition to the role of firn in thermally isolating underlying glacial ice, it defines near-surface elastic and density structure and strongly...

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Bibliographic Details
Published in:Journal of glaciology 2022-08, Vol.68 (270), p.785-798
Main Authors: Chaput, Julien, Aster, Rick, Karplus, Marianne, Nakata, Nori
Format: Article
Language:English
Subjects:
Antarctic glaciology
Antarctic ice sheet
Anthropogenic factors
Arrays
Basins
Cross correlation
Density gradients
Firn
Glaciation
Glacier ice
Human influences
Ice sheets
Particle motion
Peak frequency
Perturbation
polar firn
Propagation
Rayleigh waves
Seismic activity
Seismic data
Seismographs
Seismological data
seismology
Snow
Surface waves
Velocity
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Summary:Firn is the pervasive surface material across Antarctica, and its structures reflect its formation and history in response to environmental perturbations. In addition to the role of firn in thermally isolating underlying glacial ice, it defines near-surface elastic and density structure and strongly influences high-frequency (> 5 Hz) seismic phenomena observed near the surface. We investigate high-frequency seismic data collected with an array of seismographs deployed on the West Antarctic Ice Sheet (WAIS) near WAIS Divide camp in January 2019. Cross-correlations of anthropogenic noise originating from the approximately 5 km-distant camp were constructed using a 1 km-diameter circular array of 22 seismographs. We distinguish three Rayleigh (elastic surface) wave modes at frequencies up to 50 Hz that exhibit systematic spatially varying particle motion characteristics. The horizontal-to-vertical ratio for the second mode shows a spatial pattern of peak frequencies that matches particle motion transitions for both the fundamental and second Rayleigh modes. This pattern is further evident in the appearance of narrow band spectral peaks. We find that shallow lateral structural variations are consistent with these observations, and model spectral peaks as Rayleigh wave amplifications within similarly scaled shallow basin-like structures delineated by the strong velocity and density gradients typical of Antarctic firn.
ISSN:0022-1430
1727-5652
DOI:10.1017/jog.2021.135