Glacier processes from seismic recordings on Sørsdal Glacier, East Antarctica

Jared Carl Magyar, Anya M. Reading, Ross J. Turner, Sue Cook, Bernd Kulessa, Sarah S Thompson, Ian D Kelly, Christian Schoof

A catalogue of seismic events is produced and analysed for Sørsdal Glacier, East Antarctica. Recordings were made using an irregular array of three broadband and eight short-period seismometers, with approximately 3 km aperture, deployed slightly upstream of the expected grounding line during the 2017-18 austral summer. The broadband sensors were used to construct the event catalogue, and the short-period instruments used to aid constraints on source directionality relative to the array. We observe a diurnal cycle of seismicity, which is characterised by Rayleigh waves with peak activity corresponding to low surface temperature, indicating surface crevassing enhanced by thermal stress as the dominant source mechanism. Event groups were formed using manual analysis, followed by template matching. These groups revealed spatial and temporal clusters with distinct crevassing zones operating in diurnal cycles, and other near-surface sources with weaker periodicity potentially originating from firn or hydrological processes. These cycles and source variability show the evolution of the surface on daily and season timescales, so may provide useful insights on hydrofracture and ice shelf stability. The analysis techniques and workflows employed are transferrable to other polar ice sheet outlet glaciers where seismicity is generated largely outside the aperture of the array.