Case study of combined marine- and land-based passive seismic surveying in front of Nordenskiöldbreen outlet glacier, Adolfbukta, Svalbard

Abstract

Glaciers generate seismic waves due to calving and fracturing, meaning that recording and following event classification can be used to monitor glacier dynamics. Our aim with this study is to analyse seismic data acquired at the seabed and on land in front of Nordenskiöldbreen on Svalbard during 8 days in October 2020. The survey included 27 ocean bottom nodes, each equipped with 3 geophones and a hydrophone, and 101 land-based geophones. The resulting data contain numerous seismic P-, S- and Scholte wave events throughout the study period, as well as non-seismic gravity waves. The recording quality strongly depends on receiver type and location, especially for the latter wave types. Our results demonstrate that hydrophones at the seabed are advantageous to record gravity waves, and that Scholte waves are only recorded close to the glacier. The Scholte waves are used to estimate the near-surface S-wave profile of the seabed sediments, and the gravity wave amplitudes are converted to wave heights at the surface. We further discuss possible source mechanisms for the recorded events and present evidence that waves from earthquakes, calving and brittle fracturing of the glacier and icebergs are all represented in the data. The interpretation is based on frequency content, duration, seismic velocities and onset (emergent/impulsive) and is supported by source localization, which we show is challenging for this dataset. In conclusion, our study demonstrates the potential of using seismic observations for detecting glacier-related events and provides valuable knowledge about the importance of survey geometry, particularly the advantages of including seabed receivers in the vicinity of the glacier.