Subglacial volcano monitoring with fibre-optic sensing: Grímsvötn, Iceland

• Published in: Volcanica
• Main Authors: Sara Klaasen, Solvi Thrastarson, Yeşim Çubuk-Sabuncu, Kristín Jónsdóttir, Lars Gebraad, Patrick Paitz, Andreas Fichtner
• Format: Article in Journal/Newspaper
• Language: English
• Published: Volcanica 2023
• Subjects: seismic activity; subglacial; active volcanoes; monitoring; volcano-seismology; Geology; QE1-996.5; Ice Sheet; Iceland
• Online Access: https://doi.org/10.30909/vol.06.02.301311; https://doaj.org/article/1fada8d2c5bd4753b38a4066931652f8

We present a distributed acoustic sensing (DAS) experiment at Grímsvötn, Iceland. This is intended to investigate volcano-microseismicity at Grímsvötn specifically, and to assess the suitability of DAS as a subglacial volcano monitoring tool in general. In spring 2021, we trenched a 12 km long fiber-optic cable into the ice sheet around and within the caldera, followed by nearly one month of continuous recording. An image processing algorithm that exploits spatial coherence in DAS data detects on average ~100 events per day, almost 2 orders of magnitude more than in the regional earthquake catalog. A nonlinear Bayesian inversion reveals the presence of pronounced seismicity clusters, containing events with magnitudes between −3.4 and 1.7. Their close proximity to surface volcanic features suggests a geothermal origin. In addition to painting a fine-scale picture of seismic activity at Grímsvötn, this work confirms the potential of DAS in subglacial volcano monitoring.