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Not all Icequakes are Created Equal: Basal Icequakes Suggest Diverse Bed Deformation Mechanisms at Rutford Ice Stream, West Antarctica / Sofia‐Katerina Kufner, Alex M. Brisbourne, Andrew M. Smith, Thomas S. Hudson, Tavi Murray, REbecca Schlegel, John M. Kendall, Sridhar Anandakrishnan, Ian Lee

Journal of Geophysical Research: Earth Surface, Volume: 126, Issue: 3

Swansea University Authors: Tavi Murray, REbecca Schlegel

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DOI (Published version): 10.1029/2020jf006001

Abstract

Microseismicity, induced by the sliding of a glacier over its bed, can be used to characterize frictional properties of the ice-bed interface, which are a key parameter controlling ice stream flow. We use naturally occurring seismicity to monitor spatiotemporally varying bed properties at Rutford Ic...

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Published in: Journal of Geophysical Research: Earth Surface
ISSN: 2169-9003 2169-9011
Published: American Geophysical Union (AGU) 2021
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URI: https://cronfa.swan.ac.uk/Record/cronfa57683
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We use naturally occurring seismicity to monitor spatiotemporally varying bed properties at Rutford Ice Stream, West Antarctica. We locate 230,000 micro-earthquakes with local magnitudes from &#x2212;2.0 to &#x2212;0.3 using 90 days of recordings from a 35-station seismic network located &#x223C;40 km upstream of the grounding line. Events exclusively occur near the ice-bed interface and indicate predominantly flow-parallel stick-slip. They mostly lie within a region of interpreted stiff till and along the likely stiffer part of mega-scale glacial lineations. Within these regions, micro-earthquakes occur in spatially (&lt;100 m radius) and temporally (mostly 1&#x2013;5 days activity) restricted event-clusters (up to 4,000 events), which exhibit an increase, followed by a decrease, in event magnitude with time. This may indicate event triggering once activity is initiated. Although ocean tides modulate the surface ice flow velocity, we observe little periodic variation in overall event frequency over time and conclude that water content, bed topography and stiffness are the major factors controlling microseismicity. Based on variable rupture mechanisms and spatiotemporal characteristics, we suggest the event-clusters relate to three end-member types of bed deformation: (1) continuous creation and seismogenic destruction of small-scale bed-roughness, (2) ploughed clasts, and (3) flow-oblique deformation during landform formation or along bedrock outcrops. 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spelling 2021-12-01T11:49:57.3407629 v2 57683 2021-08-24 Not all Icequakes are Created Equal: Basal Icequakes Suggest Diverse Bed Deformation Mechanisms at Rutford Ice Stream, West Antarctica 8d6e71df690e725cd44191006dac31da 0000-0001-6714-6512 Tavi Murray Tavi Murray true false 413f0697ac45c41cbb8f45aa60e4ff71 REbecca Schlegel REbecca Schlegel true false 2021-08-24 SGE Microseismicity, induced by the sliding of a glacier over its bed, can be used to characterize frictional properties of the ice-bed interface, which are a key parameter controlling ice stream flow. We use naturally occurring seismicity to monitor spatiotemporally varying bed properties at Rutford Ice Stream, West Antarctica. We locate 230,000 micro-earthquakes with local magnitudes from −2.0 to −0.3 using 90 days of recordings from a 35-station seismic network located ∼40 km upstream of the grounding line. Events exclusively occur near the ice-bed interface and indicate predominantly flow-parallel stick-slip. They mostly lie within a region of interpreted stiff till and along the likely stiffer part of mega-scale glacial lineations. Within these regions, micro-earthquakes occur in spatially (<100 m radius) and temporally (mostly 1–5 days activity) restricted event-clusters (up to 4,000 events), which exhibit an increase, followed by a decrease, in event magnitude with time. This may indicate event triggering once activity is initiated. Although ocean tides modulate the surface ice flow velocity, we observe little periodic variation in overall event frequency over time and conclude that water content, bed topography and stiffness are the major factors controlling microseismicity. Based on variable rupture mechanisms and spatiotemporal characteristics, we suggest the event-clusters relate to three end-member types of bed deformation: (1) continuous creation and seismogenic destruction of small-scale bed-roughness, (2) ploughed clasts, and (3) flow-oblique deformation during landform formation or along bedrock outcrops. This indicates that multiple processes, simultaneously active during glacial sliding, can accommodate stick-slip behavior and that the bed continuously reorganizes. Journal Article Journal of Geophysical Research: Earth Surface 126 3 American Geophysical Union (AGU) 2169-9003 2169-9011 26 3 2021 2021-03-26 10.1029/2020jf006001 COLLEGE NANME Geography COLLEGE CODE SGE Swansea University This work was funded by NERC AFI award numbers NE/G014159/1 and NE/G013187/1 2021-12-01T11:49:57.3407629 2021-08-24T11:36:40.4249687 College of Science Geography Sofia‐Katerina Kufner 1 Alex M. Brisbourne 2 Andrew M. Smith 3 Thomas S. Hudson 4 Tavi Murray 0000-0001-6714-6512 5 REbecca Schlegel 6 John M. Kendall 7 Sridhar Anandakrishnan 8 Ian Lee 9 57683__20696__432e259873e64b8597b037858cd3bba0.pdf 57683.pdf 2021-08-24T12:11:15.4847276 Output 8012608 application/pdf Version of Record true © 2021 The Authors. This is an open access article under the terms of the Creative Commons Attribution License true eng http://creativecommons.org/licenses/by/4.0/
title Not all Icequakes are Created Equal: Basal Icequakes Suggest Diverse Bed Deformation Mechanisms at Rutford Ice Stream, West Antarctica
spellingShingle Not all Icequakes are Created Equal: Basal Icequakes Suggest Diverse Bed Deformation Mechanisms at Rutford Ice Stream, West Antarctica
Tavi, Murray
REbecca, Schlegel
title_short Not all Icequakes are Created Equal: Basal Icequakes Suggest Diverse Bed Deformation Mechanisms at Rutford Ice Stream, West Antarctica
title_full Not all Icequakes are Created Equal: Basal Icequakes Suggest Diverse Bed Deformation Mechanisms at Rutford Ice Stream, West Antarctica
title_fullStr Not all Icequakes are Created Equal: Basal Icequakes Suggest Diverse Bed Deformation Mechanisms at Rutford Ice Stream, West Antarctica
title_full_unstemmed Not all Icequakes are Created Equal: Basal Icequakes Suggest Diverse Bed Deformation Mechanisms at Rutford Ice Stream, West Antarctica
title_sort Not all Icequakes are Created Equal: Basal Icequakes Suggest Diverse Bed Deformation Mechanisms at Rutford Ice Stream, West Antarctica
author_id_str_mv 8d6e71df690e725cd44191006dac31da
413f0697ac45c41cbb8f45aa60e4ff71
author_id_fullname_str_mv 8d6e71df690e725cd44191006dac31da_***_Tavi, Murray
413f0697ac45c41cbb8f45aa60e4ff71_***_REbecca, Schlegel
author Tavi, Murray
REbecca, Schlegel
author2 Sofia‐Katerina Kufner
Alex M. Brisbourne
Andrew M. Smith
Thomas S. Hudson
Tavi Murray
REbecca Schlegel
John M. Kendall
Sridhar Anandakrishnan
Ian Lee
format Journal article
container_title Journal of Geophysical Research: Earth Surface
container_volume 126
container_issue 3
publishDate 2021
institution Swansea University
issn 2169-9003
2169-9011
doi_str_mv 10.1029/2020jf006001
publisher American Geophysical Union (AGU)
college_str College of Science
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hierarchy_top_id collegeofscience
hierarchy_top_title College of Science
hierarchy_parent_id collegeofscience
hierarchy_parent_title College of Science
department_str Geography{{{_:::_}}}College of Science{{{_:::_}}}Geography
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description Microseismicity, induced by the sliding of a glacier over its bed, can be used to characterize frictional properties of the ice-bed interface, which are a key parameter controlling ice stream flow. We use naturally occurring seismicity to monitor spatiotemporally varying bed properties at Rutford Ice Stream, West Antarctica. We locate 230,000 micro-earthquakes with local magnitudes from −2.0 to −0.3 using 90 days of recordings from a 35-station seismic network located ∼40 km upstream of the grounding line. Events exclusively occur near the ice-bed interface and indicate predominantly flow-parallel stick-slip. They mostly lie within a region of interpreted stiff till and along the likely stiffer part of mega-scale glacial lineations. Within these regions, micro-earthquakes occur in spatially (<100 m radius) and temporally (mostly 1–5 days activity) restricted event-clusters (up to 4,000 events), which exhibit an increase, followed by a decrease, in event magnitude with time. This may indicate event triggering once activity is initiated. Although ocean tides modulate the surface ice flow velocity, we observe little periodic variation in overall event frequency over time and conclude that water content, bed topography and stiffness are the major factors controlling microseismicity. Based on variable rupture mechanisms and spatiotemporal characteristics, we suggest the event-clusters relate to three end-member types of bed deformation: (1) continuous creation and seismogenic destruction of small-scale bed-roughness, (2) ploughed clasts, and (3) flow-oblique deformation during landform formation or along bedrock outcrops. This indicates that multiple processes, simultaneously active during glacial sliding, can accommodate stick-slip behavior and that the bed continuously reorganizes.
published_date 2021-03-26T04:24:17Z
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