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Repeating Icequakes at the Grounding Line of Rutford Ice Stream, West Antarctica
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  • Ian Lee,
  • Sridhar Anandakrishnan,
  • Richard Alley,
  • Sofia-Katerina Kufner,
  • Andrew Smith,
  • Alex Brisbourne
Ian Lee
Pennsylvania State University

Corresponding Author:[email protected]

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Sridhar Anandakrishnan
Pennsylvania State University
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Richard Alley
Pennsylvania State University
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Sofia-Katerina Kufner
NERC British Antarctic Survey
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Andrew Smith
NERC British Antarctic Survey
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Alex Brisbourne
NERC British Antarctic Survey
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Abstract

Basal microseisms in Antarctica, or icequakes, are valuable data sources that we can use to determine features and processes at the bed to improve our understanding of ice flow dynamics in the region. In the 2018/19 austral summer, we collaborated with the British Antarctic Survey (BAS) to deploy several seismic arrays of short period instruments over ~2 months in Rutford Ice Stream in West Antarctica to monitor natural source seismicity. During this recording period, we detected several swarms of repeating icequakes (~40 s interevent time) at our grounding line array that originate from a common basal source, which we hypothesize to be stick-slip motion over sticky spots/asperities. Smaller scale repeating icequakes, both in terms of amplitude and interevent times, also exist among the original larger repeating icequakes and are also hypothesized to originate from multiple smaller sticky spots that had less consistent loading and slipping. We built an auto-picker to detect these repeating icequakes over our recording period and located them using the automatic earthquake location Python package QuakeMigrate, and here we present our results as well as what they tell us about the basal topography. Further investigation of the interevent offsets between repeating signals of varying amplitudes and their frequency characteristics via FFT will provide more insights into the basal features, which we will corroborate with GPR basal topography data. Relations of the repeating icequakes to aseismic slip and tides will also be investigated. The findings at our grounding line array, where the repeating icequakes were first detected, can later support similar searches at the inland arrays. Antarctic ice streams remain a major source of uncertainty in projections of sea level rise, and our work seeks to constrain this uncertainty by improving our understanding of ice stream dynamics through basal conditions.