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Laboratory Experiments on Gas-Driven Volcanic Tremor and Long Period Seismicity

Volcanic tremor and long-period (LP) events are seismic signals linked to magmatic/hydrothermal fluid processes. Previous theoretical research suggests that the accumulation of gas beneath permeable caps within the shallow volcanic conduit leads to spontaneous pressure oscillations that can produce volcanic tremor and LP events (Girona et al., 2019; https://doi.org/10.1029/2019JB017482). Here we explore experimentally this hypothesis as a function of gas flux and geometry and permeability of the permeable cap. We devised an experimental setup comprising a vertically-arranged cylindrical pipe (4 cm internal diameter) which, from base to top, includes: 1) a water infill; 2) an air pocket; 3) a permeable cap; and 4) an upper pipe open to air. We injected air into the water at the base of the pipe using a set of gas flow meters and monitored pressure oscillations in the air pocket beneath the permeable cap, tracked vibrations (acceleration) of the pipe, and recorded pressure signals in the upper pipe above the cap using a microphone. Different permeability, pore arrangements, and thickness of the cap were explored. Preliminary results show that gas flow through the water without permeable cap generates low-frequency pressure oscillation (< 1~5 Hz) in the free air above, potentially related to bubble bursts. In the presence of the permeable cap, pressure oscillations in the 2-150 Hz frequency band appear in the air pocket beneath the cap, implying resonance due to gas accumulation. Different characteristics of the porous media, such as straight capillary pores and spongy materials with varying permeability, generate distinct waveform features, including different vibrations and microphone signals. For example, gas flow through straight capillary pores exhibits periodic peaks in microphone records, suggesting that permeable gas flow may control periodic volcanic outgassing. Our study offers a laboratory approach to unveil the seismoacoustic signals linked to gas circulation within porous media and serves as a reference for explaining volcano monitoring signals in natural settings.

Session: Seismoacoustic, Geodetic and Other Geophysical Investigations of Active Volcanoes [Poster Session]

Type: Poster

Room: Exhibit Hall

Date: 5/3/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Kyungmin Kim

Student Presenter: Yes

Additional Authors