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Precursory ground deformation of the 2018 phreatic eruption on Iwo-Yama volcano, revealed by four-dimensional joint analysis of airborne and spaceborne InSAR

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Title: Precursory ground deformation of the 2018 phreatic eruption on Iwo-Yama volcano, revealed by four-dimensional joint analysis of airborne and spaceborne InSAR
Authors: Narita, Shohei Browse this author
Ozawa, Taku Browse this author
Aoki, Yosuke Browse this author
Shimada, Masanobu Browse this author
Furuya, Masato Browse this author
Takada, Youichiro Browse this author
Murakami, Makoto Browse this author →KAKEN DB
Keywords: InSAR
Phreatic eruption
Ground inflation
Volcanic hydrothermal system
Airborne SAR
Issue Date: 9-Oct-2020
Publisher: Springer
Journal Title: Earth planets and space
Volume: 72
Issue: 1
Start Page: 145
Publisher DOI: 10.1186/s40623-020-01280-5
Abstract: We present detailed maps of local-scale 3D deformation preceding the 2018 phreatic eruption at Iwo-yama volcano (south of Kyushu Island, Japan), using a combination of airborne and spaceborne Interferometric Synthetic Aperture Radar (InSAR) data. The 3D and 2.5D deformation maps obtained at different periods allow us to successfully track their spatiotemporal evolution and to infer the transition of subsurface conditions responsible for the precursory deformation observed from 2014 to 2018. From 2014 to 2016, ground inflation depicted an axisymmetric pattern with the maximum displacement at the center of the deformed area. However, from 2016 to 2018, an inflation peak moved to the southern edge of the area deformed during 2014-2016 and became more localized, which was close to the newly generated vents in the 2018 eruption. Modeling of the inflations suggests that pressurization within a crack at a depth of 150 m beneath the Iwo-yama geothermal area caused the 2014-2016 deformation and had continued until the 2018 eruption. Modeling results highlight the persistence of the local ground inflation pattern just above the southern edge of the crack, which suggests the presence of a shallower inflation source contributing to the local inflation. Consequently, we interpret the sequence of these deformations as follows: from 2014, deeper-rooted fluid started to inject into a fluid-saturated crack at 150-m depth, which caused the 2014-2016 deformation. Then, after 2016, the crack inflation continued because of the continuous fluid injection and formed another pressurized part directly above the southern tip of the crack. Additionally, the results of the time-series analysis of the satellite InSAR data revealed that the local inflation started around April 2017 for which thermal activity including a mud emission became pronounced around the location of the local inflation. As a result of an episodic increase in supply rate of magmatic fluids from a deep magma reservoir from early 2018, a phreatic eruption finally occurred in the vicinity of the most deformed point, providing a clue for predicting future eruption sites, as was also observed in the Hakone 2015 eruption.
Type: article
Appears in Collections:理学院・理学研究院 (Graduate School of Science / Faculty of Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

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