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Investigating volcanic tremor and long-period seismic events through experiments on porous media gas flow

Kyungmin Kim 1, Laura Spina2, Jacopo Taddeucci2, Francesco Pennacchia2, Chiara Cornelio2, Elena Spagnuolo2, Társilo Girona1

  • Affiliations: 1Alaska Volcano Observatory, Geophysical Institute, University of Alaska Fairbanks, Fairbanks, AK, USA; 2Istituto Nazionale Di Geofisica E Vulcanologia, Sezione di Roma1, Rome, Italy 

  • Presentation type: Poster

  • Presentation time: Thursday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 132

  • Programme No: 2.1.42

  • Theme 2 > Session 1

Abstract

Volcanic tremor and long-period (LP) events are seismic signals thought to be associated with the circulation of magma and/or hydrothermal fluids. According to the gas pocket model by Girona et al. (2019), gas accumulating beneath permeable caps in shallow conduits can trigger spontaneous pressure oscillations that produce tremor and LP events. However, analytical solutions are not available to capture scenarios dominated by inertial effects (Forchheimer's law), and comparisons of seismo-acoustic signal with and without permeable caps (e.g., bubbly flow) remain limited. To address these gaps, we designed an experimental setup that simulates gas-driven volcanic seismo-acoustic signals. The system comprises a vertical cylindrical pipe (4 cm i.d.) containing, from the bottom to the top, water, an air pocket, a permeable cap, and an upper section open to the atmosphere. Air is injected at the pipe's base through flow meters, while we measure pressure in the air pocket beneath the cap, record vibrations (acceleration), and capture pressure signals above the cap with a microphone. Preliminary results show that water-only flow generates low-frequency (<1--5 Hz) pressure oscillations in the free air, with an acoustic peak near ~150 Hz, suggesting a Helmholtz resonance. In contrast, adding a porous medium above water and gas pocket yields pressure oscillations up to ~100 Hz and acoustic peaks at 0--1 Hz, indicating combined effects of water flow and porous media. Scaling analyses will allow comparing results with natural scenarios accounting for varying conduit diameters and viscosities, aiming to improve the interpretation of signals in real settings.