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Observations From an Active Seismic Distributed Acoustic Sensing Survey, Combatant Col, British Columbia

Description: 

Active seismic surveys in glaciological settings can provide insights into glacier thickness, basal structure, and glacier-bed interface conditions. These surveys often require large investments in instrumentation, personnel, and camp infrastructure; however, distributed optical fiber sensing provides a stable, low maintenance platform for high spatio-temporal seismic sampling of the cryosphere. In conjunction with ice core drilling, opportunistic distributed acoustic sensing (DAS) deployments may be performed down remnant boreholes once ice cores are retrieved. Here, we present results of an active seismic survey conducted using Betsy Gun® seismic sources on a high alpine glacier in British Columbia. A Sintela Onyx DAS interrogator was used to sample both a borehole deployed cable and surface deployed cable. The borehole fiber extended ~218 m deep into the glacier ice and the surface cable extended ~300 m from the borehole. Seismic shots were placed in ~1 m deep boreholes drilled in wet surface snow along the surface fiber route and in boreholes spaced ~100 m radially away from the borehole fiber. In addition to active seismics, Combatant Col hosts many passive seismic events such as rockfall and avalanches originating from nearby Mt. Waddington and Mt. Combatant. Preliminary investigations reveal resonant borehole tube waves likely caused by nearby passive seismic sources. Rayleigh wave dispersion is also evident on surface trenched cable. These observations show promise for modeling glacier ice thickness and revealing glacier-bed interface characteristics currently elusive in this area.

Session: Applications and Discoveries in Cryoseismology Across Spatial and Temporal Scales - I

Type: Oral

Date: 5/2/2024

Presentation Time: 04:45 PM (local time)

Presenting Author: John-Morgan

Student Presenter: Yes

Invited Presentation: 

Authors