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.