Distributed Acoustic Sensing in Volcano-Glacial Environments - Mount
Meager, British Columbia
Abstract
We demonstrate the logistic feasibility and scientific potential of
Distributed Acoustic Sensing (DAS) in alpine volcano-glacial
environments that are subject to a broad range of natural hazards. Our
work considers the Mount Meager massif, an active volcanic complex in
British Columbia, estimated to have the largest geothermal potential in
Canada, and home of Canada’s largest recorded landslide in 2010. From
September to October 2019, we acquired continuous strain data, using a 3
km long fiber-optic cable, deployed on a ridge of Mount Meager and on
the uppermost part of a glacier above 2000 m altitude. The data analysis
detected a broad range of unexpectedly intense, low-magnitude, local
seismicity. The most prominent events include long-lasting,
intermediate-frequency (0.01 - 1 Hz) tremor, and high-frequency (5 - 45
Hz) earthquakes that form distinct spatial clusters and often repeat
with nearly identical waveforms. We conservatively estimate that the
number of detectable high-frequency events varied between several tens
and nearly 400 per day. We also develop a beamforming algorithm that
uses the signal-to-noise ratio (SNR) of individual channels, and
implicitly takes the direction-dependent sensitivity of DAS into
account. Both the tremor and the high-frequency earthquakes are most
likely related to fluid movement within Mount Meager’s geothermal
reservoir. Our work illustrates that DAS carries the potential to reveal
previously undiscovered seismicity in challenging environments, where
comparably dense arrays of conventional seismometers are difficult to
install. We hope that the logistics and deployment details provided here
may serve as a starting point for future DAS experiments.