Diurnal seismicity cycle linked to subsurface melting on an ice shelf

Douglas R. Macayeal*, Alison F. Banwell, Emile A Okal, Jinqiao Lin, Ian C. Willis, Becky Goodsell, Grant J. Macdonald

*Corresponding author for this work

Research output: Contribution to journalArticle

6 Scopus citations

Abstract

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 and flexural-gravity waves at frequency. 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.

Original languageEnglish (US)
Pages (from-to)137-157
Number of pages21
JournalAnnals of Glaciology
Volume60
Issue number79
DOIs
StatePublished - Sep 1 2019

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Keywords

  • Antarctic glaciology
  • debris-covered glaciers
  • ice shelves
  • ice temperature
  • seismics

ASJC Scopus subject areas

  • Earth-Surface Processes

Cite this

Macayeal, D. R., Banwell, A. F., Okal, E. A., Lin, J., Willis, I. C., Goodsell, B., & Macdonald, G. J. (2019). Diurnal seismicity cycle linked to subsurface melting on an ice shelf. Annals of Glaciology, 60(79), 137-157. https://doi.org/10.1017/aog.2018.29