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Tracking Volcanic State Transitions Through Seismic Velocity Changes: Insights from Askja, Aso, and Gareloi Volcanoes

Laure Brenot 1, Corentin Caudron1, Thomas Lecocq2, Alexander Yates1, Raphael De Plaen2, Laura Ermert3, Társilo Girona4, Tom Winder5, Matt Haney6, Nicholas Rawlinson7, Yixiao Sheng3, Aurélien Mordret8, Florent Brenguier3, Martanto1, Yosuke Aoki9, Kristín Jónsdóttir10

  • Affiliations: 1G-Time, Université Libre de Bruxelles, Brussels, Belgium; 2Royal Observatory of Belgium, Brussels, Belgium; 3ISTerre, Université Grenoble Alpes, Grenoble, France; 4Alaska Volcano Observatory, Geophysical Institute, University of Alaska Fairbanks, Fairbanks, USA; 5University of Iceland, Reykjavík, Iceland; 6U.S. Geological Survey, Alaska Volcano Observatory, Anchorage, USA; 7Department of Earth Sciences -- Bullard Labs, University of Cambridge, Cambridge, UK; 8Department of Geophysics and Sedimentary Basins, Geological Survey of Denmark and Greenland, Copenhagen, Denmark; 9Earthquake Research Institute, University of Tokyo, Tokyo, Japan; 10Icelandic Meteorological Office, Reykjavík, Iceland.

  • Presentation type: Talk

  • Presentation time: Friday 15:00 - 15:15, Room S160

  • Programme No: 2.1.11

  • Theme 2 > Session 1

Abstract

Identifying the transition from volcanic quiescence to unrest remains a critical challenge in volcano monitoring. This study advances our understanding of volcanic state transitions by analyzing continuous seismic records from three volcanic systems: Askja (Iceland), Aso (Japan), and Gareloi (Alaska, USA). We employ a multi-parametric approach combining seismic velocity changes (dv/v), kernel sensitivity analysis, and seismic attenuation measurements to track subsurface evolution over time. We integrate ambient noise cross-correlation using MSNoise to compute attenuation and detect seismic velocity changes, with source locations constrained by surface wave kernel sensitivity across different frequencies and velocity models. Results show distinct patterns of unrest across sites. At Askja, we detected a pronounced decrease in dv/v at approximately 2 km depth in August 2021, concomitant with increased attenuation, shallow microseismicity, and the initiation of surface uplift (80 cm over three years). At Aso, the 2016 Kumamoto earthquake induced an immediate 0.5% decrease in dv/v, followed by a healing process and increased attenuation, interrupted six months later by an eruption marked by 0.3% dv/v decrease. At Gareloi, 2021 seismic unrest is characterized by tremor and persistent long-period events over three months, corresponding with a 1% dv/v decrease at roughly 3 km depth. These diverse case studies demonstrate how continuous monitoring of seismic velocity changes and attenuation reveals both gradual and sudden transitions in volcanic systems. In addition, our findings establish baseline behaviors for these volcanoes and highlight characteristic seismic signatures associated with unrest, thereby advancing our capability to detect and interpret potential precursors to volcanic eruptions.