Fiber-optic observation of volcanic tremor through floating ice sheet resonance

Entirely covered by the Vatnajökull ice cap, Grímsvötn is among Iceland's largest and most hazardous volcanoes. Here we demonstrate that fiber-optic sensing technology deployed on a natural floating ice resonator can detect volcanic tremor at the level of few nanostrain/s, thereby enabling a ne...

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Bibliographic Details
Published in:The Seismic record 2022-07, Vol.2 (3), p.148-155
Main Authors: Fichtner, Andreas, Klaasen, Sara, Thrastarson, Solvi, Cubuk-Sabuncu, Yesim, Paitz, Patrick, Jonsdottir, Kristin
Format: Article
Language:English
Subjects:
acoustical waves
detection
distributed acoustic sensing
earthquakes
eruptions
Europe
fiber optics
fissures
flexure
floods
geologic hazards
glacial geology
global navigation satellite systems
Global Positioning System
Grimsvotn
ice
ice sheets
Iceland
instruments
monitoring
natural hazards
oscillations
prediction
propagation
Quaternary geology
resonance
risk management
sea ice
Seismology
subarctic regions
temporal distribution
variations
Vatnajokull
vibration
volcanic earthquakes
Western Europe
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Summary:Entirely covered by the Vatnajökull ice cap, Grímsvötn is among Iceland's largest and most hazardous volcanoes. Here we demonstrate that fiber-optic sensing technology deployed on a natural floating ice resonator can detect volcanic tremor at the level of few nanostrain/s, thereby enabling a new mode of subglacial volcano monitoring under harsh conditions. A 12.5 km long fiber-optic cable deployed on Grímsvötn in May 2021 revealed a high level of local earthquake activity, superimposed onto nearly monochromatic oscillations of the caldera. High data quality combined with dense spatial sampling identify these oscillations as flexural gravity wave resonance of the ice sheet that floats atop a subglacial lake. Although being affected by the ambient wavefield, the time-frequency characteristics of observed caldera resonance require the presence of an additional persistent driving force with temporal variations over several days, that is most plausibly explained in terms of low-frequency volcanic tremor. In addition to demonstrating the logistical feasibility of installing a large, high-quality fiber-optic sensing network in a subarctic environment, our experiment shows that ice sheet resonance may act as a natural amplifier of otherwise undetectable (volcanic) signals. This suggests that similar resonators might be used in a targeted fashion to improve monitoring of ice-covered volcanic systems.
ISSN:2694-4006
2694-4006
DOI:10.1785/0320220010