Ice-core break-off as an opportunistic seismic source on the Northeast Greenland Ice Stream

Abstract. Ice-core drilling generates repeated mechanical disturbances within the ice column, raising the possibility that operational drilling signals could be used as opportunistic seismic sources. We test whether impulsive ice-core break-off events during the 2022 EastGRIP (Greenland) field season can be detected on surface-based, near-offset three-component geophones and used to estimate apparent P-wave velocity. A catalogue of 67 candidate core-break times was identified from drill-log load peaks, of which 37 had sufficient simultaneous near-offset seismic station coverage for assessment. Only three of these assessable events produced plausible impulsive arrivals. Automatic STA/LTA triggering was useful for identifying candidate windows, but did not reliably pick first arrivals. Where clear arrivals were identifiable above the background noise, manually picked arrivals gave apparent P-wave velocities consistent with firn/ice propagation, and showed a small across-flow faster-than-along-flow tendency, though this difference remains below the level of uncertainty required for robust anisotropy interpretation. These results show that ice-core break-off may provide a useful opportunistic seismic source, but only if future deployments include direct source-time measurement, quiet acquisition conditions, and receiver geometries designed for this purpose.