Diurnal seismicity cycle linked to subsurface melting on an ice shelf
<jats:title>ABSTRACT</jats:title><jats:p>Seismograms acquired on the McMurdo Ice Shelf, Antarctica, during an Austral summer melt season (November 2016–January 2017) reveal a diurnal cycle of seismicity, consisting of hundreds of thousands of small ice quakes limited to a 6–12 hour...
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ftunivcam:oai:www.repository.cam.ac.uk:1810/286514 2024-01-14T10:00:03+01:00 Diurnal seismicity cycle linked to subsurface melting on an ice shelf Macayeal, DR Banwell, AF Okal, EA Lin, J Willis, IC Goodsell, B Macdonald, GJ 2019 application/pdf https://www.repository.cam.ac.uk/handle/1810/286514 https://doi.org/10.17863/CAM.33824 eng eng Cambridge University Press (CUP) http://dx.doi.org/10.1017/aog.2018.29 Annals of Glaciology https://www.repository.cam.ac.uk/handle/1810/286514 doi:10.17863/CAM.33824 Antarctic glaciology debris-covered glaciers ice shelves ice temperature seismics Article 2019 ftunivcam https://doi.org/10.17863/CAM.33824 2023-12-21T23:27:33Z <jats:title>ABSTRACT</jats:title><jats:p>Seismograms acquired on the McMurdo Ice Shelf, Antarctica, during an Austral summer melt season (November 2016–January 2017) reveal a diurnal cycle of seismicity, consisting of hundreds of thousands of small ice quakes limited to a 6–12 hour period during the evening, in an area where there is substantial subsurface melting. This cycle is explained by thermally induced bending and fracture of a frozen surface superimposed on a subsurface slush/water layer that is supported by solar radiation penetration and absorption. A simple, one-dimensional model of heat transfer driven by observed surface air temperature and shortwave absorption reproduces the presence and absence (as daily weather dictated) of the observed diurnal seismicity cycle. Seismic event statistics comparing event occurrence with amplitude suggest that the events are generated in a fractured medium featuring relatively low stresses, as is consistent with a frozen surface superimposed on subsurface slush. Waveforms of the icequakes are consistent with hydroacoustic phases at frequency <jats:inline-formula><jats:alternatives><jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="gif" xlink:type="simple" xlink:href="S0260305518000290_inline1" /><jats:tex-math>$ {\bf \gt} \bf 75\,{\bf Hz}$</jats:tex-math></jats:alternatives></jats:inline-formula> and flexural-gravity waves at frequency <jats:inline-formula><jats:alternatives><jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="gif" xlink:type="simple" xlink:href="S0260305518000290_inline2" /><jats:tex-math>$ \bf {\bf \lt}25\,{\bf Hz}$</jats:tex-math></jats:alternatives></jats:inline-formula>. Our results suggest that seismic observation may prove useful in monitoring subsurface melting in a manner that complements other ground-based methods as well as remote sensing.</jats:p> Article in Journal/Newspaper Antarc* Antarctic Antarctica Ice Shelf Ice Shelves McMurdo Ice Shelf Apollo - University of Cambridge Repository Antarctic Austral McMurdo Ice Shelf ENVELOPE(166.500,166.500,-78.000,-78.000) |
institution |
Open Polar |
collection |
Apollo - University of Cambridge Repository |
op_collection_id |
ftunivcam |
language |
English |
topic |
Antarctic glaciology debris-covered glaciers ice shelves ice temperature seismics |
spellingShingle |
Antarctic glaciology debris-covered glaciers ice shelves ice temperature seismics Macayeal, DR Banwell, AF Okal, EA Lin, J Willis, IC Goodsell, B Macdonald, GJ Diurnal seismicity cycle linked to subsurface melting on an ice shelf |
topic_facet |
Antarctic glaciology debris-covered glaciers ice shelves ice temperature seismics |
description |
<jats:title>ABSTRACT</jats:title><jats:p>Seismograms acquired on the McMurdo Ice Shelf, Antarctica, during an Austral summer melt season (November 2016–January 2017) reveal a diurnal cycle of seismicity, consisting of hundreds of thousands of small ice quakes limited to a 6–12 hour period during the evening, in an area where there is substantial subsurface melting. This cycle is explained by thermally induced bending and fracture of a frozen surface superimposed on a subsurface slush/water layer that is supported by solar radiation penetration and absorption. A simple, one-dimensional model of heat transfer driven by observed surface air temperature and shortwave absorption reproduces the presence and absence (as daily weather dictated) of the observed diurnal seismicity cycle. Seismic event statistics comparing event occurrence with amplitude suggest that the events are generated in a fractured medium featuring relatively low stresses, as is consistent with a frozen surface superimposed on subsurface slush. Waveforms of the icequakes are consistent with hydroacoustic phases at frequency <jats:inline-formula><jats:alternatives><jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="gif" xlink:type="simple" xlink:href="S0260305518000290_inline1" /><jats:tex-math>$ {\bf \gt} \bf 75\,{\bf Hz}$</jats:tex-math></jats:alternatives></jats:inline-formula> and flexural-gravity waves at frequency <jats:inline-formula><jats:alternatives><jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="gif" xlink:type="simple" xlink:href="S0260305518000290_inline2" /><jats:tex-math>$ \bf {\bf \lt}25\,{\bf Hz}$</jats:tex-math></jats:alternatives></jats:inline-formula>. Our results suggest that seismic observation may prove useful in monitoring subsurface melting in a manner that complements other ground-based methods as well as remote sensing.</jats:p> |
format |
Article in Journal/Newspaper |
author |
Macayeal, DR Banwell, AF Okal, EA Lin, J Willis, IC Goodsell, B Macdonald, GJ |
author_facet |
Macayeal, DR Banwell, AF Okal, EA Lin, J Willis, IC Goodsell, B Macdonald, GJ |
author_sort |
Macayeal, DR |
title |
Diurnal seismicity cycle linked to subsurface melting on an ice shelf |
title_short |
Diurnal seismicity cycle linked to subsurface melting on an ice shelf |
title_full |
Diurnal seismicity cycle linked to subsurface melting on an ice shelf |
title_fullStr |
Diurnal seismicity cycle linked to subsurface melting on an ice shelf |
title_full_unstemmed |
Diurnal seismicity cycle linked to subsurface melting on an ice shelf |
title_sort |
diurnal seismicity cycle linked to subsurface melting on an ice shelf |
publisher |
Cambridge University Press (CUP) |
publishDate |
2019 |
url |
https://www.repository.cam.ac.uk/handle/1810/286514 https://doi.org/10.17863/CAM.33824 |
long_lat |
ENVELOPE(166.500,166.500,-78.000,-78.000) |
geographic |
Antarctic Austral McMurdo Ice Shelf |
geographic_facet |
Antarctic Austral McMurdo Ice Shelf |
genre |
Antarc* Antarctic Antarctica Ice Shelf Ice Shelves McMurdo Ice Shelf |
genre_facet |
Antarc* Antarctic Antarctica Ice Shelf Ice Shelves McMurdo Ice Shelf |
op_relation |
https://www.repository.cam.ac.uk/handle/1810/286514 doi:10.17863/CAM.33824 |
op_doi |
https://doi.org/10.17863/CAM.33824 |
_version_ |
1788063325939040256 |