Firn Seismic Anisotropy in the North East Greenland Ice Stream from Ambient Noise Surface Waves
We analyse ambient noise seismic data from 23 three-component seismic nodes to study firn velocity structure and seismic anisotropy near the EastGRIP camp along the Northeast Greenland Ice Stream (NEGIS). Using 9-component correlation tensors, we derive dispersion curves of Rayleigh and Love wave gr...
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ftcopernicus:oai:publications.copernicus.org:egusphere115015 2024-09-15T18:04:21+00:00 Firn Seismic Anisotropy in the North East Greenland Ice Stream from Ambient Noise Surface Waves Pearce, Emma Zigone, Dimitri Hofstede, Coen Fichtner, Andreas Rimpot, Joachim Olander Rasmussen, Sune Freitag, Johannes Eisen, Olaf 2023-11-09 application/pdf https://doi.org/10.5194/egusphere-2023-2192 https://egusphere.copernicus.org/preprints/2023/egusphere-2023-2192/ eng eng doi:10.5194/egusphere-2023-2192 https://egusphere.copernicus.org/preprints/2023/egusphere-2023-2192/ eISSN: Text 2023 ftcopernicus https://doi.org/10.5194/egusphere-2023-2192 2024-08-28T05:24:15Z We analyse ambient noise seismic data from 23 three-component seismic nodes to study firn velocity structure and seismic anisotropy near the EastGRIP camp along the Northeast Greenland Ice Stream (NEGIS). Using 9-component correlation tensors, we derive dispersion curves of Rayleigh and Love wave group velocities from 3 Hz to 40 Hz. These velocity distributions exhibit anisotropy along and across the flow. To assess these variations, we invert dispersion curves for shear wave velocities (V sh and V sv ) in the top 150 m of NEGIS using a Markov Chain Monte Carlo approach. The reconstructed1-D shear velocity model reveals radial anisotropy in the firn, with V sh 12 %–15 % greater than V sv , peaking at the critical density (550 kg m –3 ). We combine density data from firn cores drilled in 2016 and 2018 to create a new density parameterisation for NEGIS, serving as a reference for our results. We link seismic anisotropy in the NEGIS to effective and intrinsic causes. Seasonal densification, wind crusts, and melt layers induce effective anisotropy, leading to faster V sh waves. Changes in firn recrystalisation cause intrinsic anisotropy, altering the V sv to V sh ratio. We observe a shallower firn-ice transition across flow (≈ 50 m) compared to along flow (≈ 60 m), suggesting increased firn compaction due to the predominant wind direction and increased deformation towards the shear margin. We demonstrate that short-duration (nine-day minimum), passive, seismic deployments, and noise-based analysis can determine seismic anisotropy in firn, and reveal 2-D firn structure and variability. Text East Greenland Greenland Copernicus Publications: E-Journals |
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Open Polar |
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Copernicus Publications: E-Journals |
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ftcopernicus |
language |
English |
description |
We analyse ambient noise seismic data from 23 three-component seismic nodes to study firn velocity structure and seismic anisotropy near the EastGRIP camp along the Northeast Greenland Ice Stream (NEGIS). Using 9-component correlation tensors, we derive dispersion curves of Rayleigh and Love wave group velocities from 3 Hz to 40 Hz. These velocity distributions exhibit anisotropy along and across the flow. To assess these variations, we invert dispersion curves for shear wave velocities (V sh and V sv ) in the top 150 m of NEGIS using a Markov Chain Monte Carlo approach. The reconstructed1-D shear velocity model reveals radial anisotropy in the firn, with V sh 12 %–15 % greater than V sv , peaking at the critical density (550 kg m –3 ). We combine density data from firn cores drilled in 2016 and 2018 to create a new density parameterisation for NEGIS, serving as a reference for our results. We link seismic anisotropy in the NEGIS to effective and intrinsic causes. Seasonal densification, wind crusts, and melt layers induce effective anisotropy, leading to faster V sh waves. Changes in firn recrystalisation cause intrinsic anisotropy, altering the V sv to V sh ratio. We observe a shallower firn-ice transition across flow (≈ 50 m) compared to along flow (≈ 60 m), suggesting increased firn compaction due to the predominant wind direction and increased deformation towards the shear margin. We demonstrate that short-duration (nine-day minimum), passive, seismic deployments, and noise-based analysis can determine seismic anisotropy in firn, and reveal 2-D firn structure and variability. |
format |
Text |
author |
Pearce, Emma Zigone, Dimitri Hofstede, Coen Fichtner, Andreas Rimpot, Joachim Olander Rasmussen, Sune Freitag, Johannes Eisen, Olaf |
spellingShingle |
Pearce, Emma Zigone, Dimitri Hofstede, Coen Fichtner, Andreas Rimpot, Joachim Olander Rasmussen, Sune Freitag, Johannes Eisen, Olaf Firn Seismic Anisotropy in the North East Greenland Ice Stream from Ambient Noise Surface Waves |
author_facet |
Pearce, Emma Zigone, Dimitri Hofstede, Coen Fichtner, Andreas Rimpot, Joachim Olander Rasmussen, Sune Freitag, Johannes Eisen, Olaf |
author_sort |
Pearce, Emma |
title |
Firn Seismic Anisotropy in the North East Greenland Ice Stream from Ambient Noise Surface Waves |
title_short |
Firn Seismic Anisotropy in the North East Greenland Ice Stream from Ambient Noise Surface Waves |
title_full |
Firn Seismic Anisotropy in the North East Greenland Ice Stream from Ambient Noise Surface Waves |
title_fullStr |
Firn Seismic Anisotropy in the North East Greenland Ice Stream from Ambient Noise Surface Waves |
title_full_unstemmed |
Firn Seismic Anisotropy in the North East Greenland Ice Stream from Ambient Noise Surface Waves |
title_sort |
firn seismic anisotropy in the north east greenland ice stream from ambient noise surface waves |
publishDate |
2023 |
url |
https://doi.org/10.5194/egusphere-2023-2192 https://egusphere.copernicus.org/preprints/2023/egusphere-2023-2192/ |
genre |
East Greenland Greenland |
genre_facet |
East Greenland Greenland |
op_source |
eISSN: |
op_relation |
doi:10.5194/egusphere-2023-2192 https://egusphere.copernicus.org/preprints/2023/egusphere-2023-2192/ |
op_doi |
https://doi.org/10.5194/egusphere-2023-2192 |
_version_ |
1810441842891685888 |