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- Title
Infrasound–Electric‐Field Coupling Associated With the 2018 Shinmoe‐Dake Eruptions, Kirishima Volcanic Complex, Japan.
- Authors
Aniya, Satoru; Aizawa, Koki; Matsushima, Takeshi
- Abstract
Shinmoe‐dake volcano, which is within the Kirishima volcanic complex, Japan, erupted from March to June 2018. The eruptions were recorded by various geophysical instruments that were installed 3.1–5.4 km from the crater. Here we present the first documented evidence of infrasound‐induced electric‐field changes in the near surface at the time of the explosive eruptions. Significant electric‐field changes coincide with the infrasound arrivals. An order‐of‐magnitude estimation of the electric field indicates that the electrokinetic mechanism induced by pore water movement relative to the host rock, is a plausible cause of the observed infrasound–electric‐field coupling. The ground displacement and electric‐field particle motions suggest that the infrasound waves from the explosive eruptions produce vertical ground motion, and simultaneously induce horizontal groundwater flow, which subsequently generates electric‐field changes due to the propagation of the infrasound wave. Plain Language Summary: Infrasound, which is an acoustic wave that propagates through the air at frequencies below 20 Hz, produces ground vibrations. Explosive volcanic eruptions can generate a significant infrasound signal with a clear compressional phase and subsequent rarefaction phase. This infrasound signal travels at the speed of sound while producing vertical ground motion. Coincident infrasound and vertical displacement changes are detected at timescales of a few seconds using observation stations with a collocated microphone and broadband seismometer. Here we provide the first evidence that the infrasound signal from such a volcanic eruption also generates an electric current in the near surface. The electric current, which is measured using a voltmeter and electrode, is very similar to the observed infrasound signal and its associated ground motion. Local infrasound‐induced groundwater flow is a plausible cause of the observed electric current generation. Key Points: Infrasound‐induced electric‐field changes were first observed 3.1–5.4 km from the eruption craterThe electric‐field changes coincided with the infrasound arrivalsInfrasound‐ground deformation and infrasound‐electric‐field couplings are observed at the time of the explosive eruptions
- Subjects
JAPAN; EXPLOSIVE volcanic eruptions; SOIL vibration; GEOPHYSICAL instruments; VERTICAL motion; GROUNDWATER flow; SPEED of sound; ELECTRIC currents
- Publication
Geophysical Research Letters, 2022, Vol 49, Issue 3, p1
- ISSN
0094-8276
- Publication type
Article
- DOI
10.1029/2021GL096555