Distributed Acoustic Sensing in Volcano‐Glacial Environments—Mount Meager, British Columbia. Issue 11 (12th November 2021)

• Record Type: Journal Article
• Authors: Klaasen, Sara; Paitz, Patrick; Lindner, Nadja; Dettmer, Jan; Fichtner, Andreas
• Is Part Of: Journal of geophysical research. Volume 126:Issue 11(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-11-12
• Subjects: distributed acoustic sensing -- volcano seismology -- Mount Meager -- glaciology -- geothermal energy -- beamforming; Geomagnetism -- Periodicals; Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 551.1
• DOI: 10.1029/2021JB022358
• Languages: English
• ISSNs: 2169-9313

Abstract

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 2, 000 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. Plain Language Summary: Distributed acoustic sensing (DAS) is an emerging technology to measure microscopic ground motion by sending laser pulses through fiber‐optic cables, which are commonly used for telecommunication. A cable of several kilometers length provides thousands of measurement points, which can yield highly detailed information about the propagation of seismic waves excited by earthquakes. The ease of deploying a fiber‐optic cable, compared to the challenge of installing thousands of conventional seismometers, opens new opportunities for earthquake studies in remote and hazardous areas. Here, we present the first application of DAS in a volcano‐glacial environment. Mount Meager, the site of the experiment in British Columbia, is an active volcano known for its geothermal potential and for hosting the largest landslide in recorded Canadian history. Using a 3‐km‐long cable deployed on Mount Meager's ridge and glacier, we were able to detect an unexpectedly broad range of seismic signals, including up to 400 small earthquakes per day and volcanic tremor that may last for many hours. The most likely origin of these events is the movement of fluids within the geothermal reservoir, and their existence indicates that Mount Meager is substantially more active than previously thought. Key Points: We demonstrate the feasibility and potential of distributed acoustic sensing (DAS) in alpine volcano‐glacial environments The DAS experiment at Mount Meager reveals unexpected volcanic tremor and volcanic earthquake swarms related to geothermal fluids Mount Meager is significantly more active than previously estimated on the basis of conventional seismic instruments in the area