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Capturing Glacier-Wide Cryoseismicity With Distributed Acoustic Sensing

Session: Fiber-Optic Seismology I

Type: Oral

Date: 4/23/2021

Presentation Time: 10:15 AM Pacific

Description: 

Over the past 1-2 decades, seismological measurements have provided new and unique insights into glacier and ice sheet dynamics. At the same time, sensor deployment is typically limited as it requires installations in harsh environments, which are difficult to access. Distributed Acoustic Sensing (DAS) may overcome this limitation of sensor coverage in the cryosphere.

First DAS applications on the Greenland and Antarctic ice sheets and on Alpine glacier ice have highlighted the technique’s superiority. Signals of natural and man-made seismic sources can be resolved with an unrivaled level of detail offering new perspectives for studies of ice structure, basal boundary conditions and source locations. However, previous studies employed only relatively small network scales with a point-like borehole deployment or < 1 km cable aperture at the ice surface.

Here we present a DAS installation, which aims to cover the majority of an Alpine glacier catchment: For one month in summer 2020 we deployed a 9 km long fiber optic cable on Rhonegletscher, Switzerland, to gather continuous DAS data. The cable followed the glacier’s central flow line starting in the lowest kilometer of the ablation zone and extending well into the accumulation area. Even for a relatively small mountain glacier such as Rhonegletscher, cable deployment was a considerable logistical challenge. Manual cable transport via sled required installation of separate cable sections, which had to be spliced together in the field. Given high-melt conditions, the cable was simply placed on the glacier’s snow and ice surface. Nevertheless, the DAS records yielded clear signals of englacial seismic sources, which can be compared to co-located geophone and seismometer records. Moreover, the fiber optic setup is sensitive to low frequencies (< 0.1 Hz), which are difficult to capture with conventional on-ice stations in high-melt glacial regions. We discuss these signals and their possible sources together with environmental noise (wind, meltwater flow, precipitation), typical for high Alpine terrain.

Presenting Author: Fabian Walter

Student Presenter: No

Authors