Quantifying subsurface fracture damage in glaciers using fiber-optic seismology

Crevassing critically controls glacier stability. Crevasses can penetrate deep into a glacier or ice shelf, promoting calving, ice avalanches, and even sudden catastrophic ice shelf collapse. Yet quantifying subsurface fracture damage remains largely unquantified. Here, we show how distributed acoustic sensing technology can quantify subsurface fracture damage in unprecedented detail at an alpine glacier. We first demonstrate that seismic anisotropy can quantify fracture extent. We also study crevasse icequake failure mechanisms, which fail predominantly via tensile opening. Icequake-derived crevasse opening is consistent with anisotropy-derived estimates (∼8% of total ice volume), suggesting that damage is dominated by fracture rather than melt. These results establish a scalable approach for monitoring subsurface ice damage that complements existing satellite surface observations. Applications range from monitoring the stability of alpine glaciers that pose a risk to alpine communities to providing foundations for assessing subsurface fracture extent at globally pertinent ice sheets and ice shelves.