Distributed Acoustic Sensing (DAS) for natural microseismicity studies:
A case study from Antarctica
Abstract
Icequakes, microseismic earthquakes at glaciers, offer critical insights
into the dynamics of ice sheets. For the first time in the Antarctic, we
explore the use of fibre optic cables as Distributed Acoustic Sensors
(DAS) as a new approach for monitoring basal icequakes. Fibre was
deployed on the ice surface at Rutford Ice Stream, in two different
configurations. We compare the performance of DAS with a conventional
geophone network for: microseismic detection and location; resolving
source and noise spectra; source mechanism inversion; and measuring
anisotropic shear-wave splitting parameters. The DAS arrays detect fewer
events than the geophone array. However, DAS is superior to geophones
for recording the microseism signal, suggesting the applicability of DAS
for ambient noise interferometry. We also present the first
full-waveform source mechanism inversions using DAS anywhere,
successfully constraining the horizontal stick-slip nature of the
icequakes. In addition, we develop an approach to use a 2D DAS array
geometry as an effective multi-component sensor capable of accurately
characterising shear-wave splitting due to anisotropy of the ice fabric.
Although our observations originate from a glacial environment, the
methodology and implications of this work are relevant for employing DAS
in other microseismic environments.