A large-N passive seismic array on Glacier d’Argentière, France: Observations, recorded signals and potentials

Fabian Lindner*1, Florent Gimbert2, Fabian Walter1, Philippe Roux3

1Laboratory of Hydraulics, Hydrology and Glaciology, ETH Zürich, Switzerland (lindner@vaw.baug.ethz.ch), 2Institut des Géosciences de l’Environnement, Université Grenoble Alpes, France, 3Institut des Sciences de la Terre, Université Grenoble Alpes, France.

Glaciers are rich in seismicity generating signals by ice fracturing, water routing, or basal motion. The analysis of the emitted seismic signals has been proven to be valuable towards better understanding glacier dynamics. However, coverage of seismic stations in glacierized regions is often sparse due to technical limitations and because glaciers are hard to access. Recent advances in instrumentation now make it possible to deploy large-N arrays in rough environments. During the early melt season 2018 (from late April to early June), 100 3-component geophones of the French instrumentation pool were deployed by University of Grenoble on the tongue of Glacier d’Argentière, France. The sensors were arranged in a regular grid (50~m spacing) sampling the ice vibrations continuously, thereby providing one of the first dense and large-N datasets from a glacierized region.

Regarding the investigation of  glacier dynamics, Glacier d’Argentière is an ideal field site. Its long term evolution and basal motion (accessible via unique subglacial tunnel facilities) have been monitored continuously over the past decades. For the first time in such context, the deployment of the geophones enables us to “look into” the glacier with high spatial resolution. The dataset allows us to study englacial and subglacial processes in unprecedented detail but also to image and monitor the glacier’s interior and its temporal changes. We present recorded signals (which include icequakes, earthquakes, tremors, and the ambient field), evaluate the geophones’ performance, and discuss potential imaging and monitoring approaches. Regarding the latter, the dense array design permits the application of novel techniques such as seismic interferometry by multidimensional deconvolution and wavefield gradiometry.