Distributed Acoustic Sensing for the Exploration of the Mount Meager Volcanic Complex, British Columbia, Canada.

Abstract:

We present one of the first applications of Distributed Acoustic Sensing (DAS) in a volcanic environment. We use DAS to explore the Mount Meager massif, an active volcanic complex in the Garibaldi Volcanic Belt in British Columbia which is estimated to have the largest geothermal potential in Canada and caused Canada’s largest recent landslide in 2010. Additionally, receding glaciers near Mount Meager may destabilise the complex and trigger more landslides and volcanic activities, contributing to its overall hazard.

This research investigates the feasibility of DAS on volcanoes and alpine environments while also searching for active volcanic signals. A fibre-optic cable was installed at 2000 m elevation and yielded continuous measurements for one month in September/October 2019. The 3 km long cable was placed in a trench that loops around a ridge on Mount Meager and traverses the uppermost part of a glacier on firn.

The difference in the installation between sediments and firn is clearly recognisable in the data, and we can identify numerous different events after standard processing. Low-period events (0.01 – 1 Hz) last for hours and do not seem to be correlated with microseismic ocean or atmospheric noise. We speculate that these events may be volcanic tremor, even though further research is required to support this hypothesis. The noise in this frequency range is remarkably coherent among channels, resulting in virtually identical traces. In addition, we can identify thousands of high-frequency events (>5 Hz). The frequency-amplitude distributions of these events indicate a natural origin and beamforming is applied to further examine this hypothesis. A synthetic beamforming study shows that conventional beamforming can be directly applied to DAS data and can be improved by considering the signal to noise ratio of individual channels. Our initial results indicate that these high-frequency, seismic events occur in clusters and may be caused by volcanic activity.