Inter-eruptive volcanism at Usu volcano: Micro-earthquakes and dome subsidence

Aoyama, Hiroshi; Onizawa, Shin’ya; Kobayashi, T.; Tameguri, Takeshi; Hashimoto, Takeshi; Oshima, Hiromitsu; Mori, Hitoshi

doi:10.1016/j.jvolgeores.2009.09.009

Cited by 9 publications

(14 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Since the 1663 eruption, nine eruptions occurred, of which four were in the twentieth century, in 1910, 1943–1945, 1977–1982, and 2000. The composition of the erupted products evolved from rhyolitic to dacitic and the temperature of the magma apparently increased with time, possibly due to sequential tapping from a stratified magma chamber replenished with high‐temperature magma [ Tomiya and Takahashi , ; Aoyama et al , ; Matsumoto and Nakagawa , ]. Unlike the previous eruptions, the 1977–1982 eruption occurred on the summit crater: after only 36 h of precursory felt earthquakes, a large dacitic ash column of the subplinian type rose on the morning of 7 August 1977.…”

Section: Types Of Caldera Unrestmentioning

confidence: 99%

“…On 31 March, 788 volcanic earthquakes and 139 low‐frequency events occurred under a decreasing trend in the seismicity, with slow deformation near the volcano and fast deformation near the site of forthcoming eruption. On the early afternoon of 31 March, a VEI 2 eruption started on the NW slope of Mount Usu and seismic activity decreased [ Jousset et al , , and references therein; Zobin et al , ; Aoyama et al , ]. The preeruptive earthquakes, reaching a maximum magnitude of 4.6, clustered beneath the summit and southern slope of the volcano, mainly at depth between 4 and 7 km; the epicenters did not reach the sites of the forthcoming eruption but stopped at a distance of 1–3 km [ Zobin et al , ].…”

Section: Types Of Caldera Unrestmentioning

confidence: 99%

See 1 more Smart Citation

An overview of recent (1988 to 2014) caldera unrest: Knowledge and perspectives

Acocella

Lorenzo

Newhall³

et al. 2015

Reviews of Geophysics

148

165

View full text Add to dashboard Cite

Calderas are among the most active and dangerous volcanoes. Caldera unrest is defined by enhanced seismicity, gravity changes, surface deformation, and degassing. Although much caldera unrest does not lead to an eruption, every eruption is preceded by an unrest episode. Therefore, the proper description of unrest and the forecast of its possible outcome is a timely and challenging task. Here we review the best known unrest at calderas from 1988 to 2014, building on previous work and proposing an updated database. Where established, the root cause for unrest is always magmatic; none was purely hydrothermal or tectonic. An interpretive classification of unrest invokes two spectra-compositional (mafic to felsic) and the state of magma conduits feeding from the magma reservoir(s) to the surface (from fully plugged, through semiplugged, to open). Magma and gas in open conduits can rise and erupt freely; magma in semiplugged conduits erupts less frequently yet still allows some gas to escape; plugged conduits allow neither magma nor gas to escape. Unrest in mafic calderas is subtler, less pronounced, and repeated, especially with open systems, ensuring the continuous, aseismic, and moderate release of magma. Plugged felsic calderas erupt infrequently, anticipated by isolated, short and seismically active unrest. Semiplugged felsic calderas also erupt infrequently and are restless over decades or centuries, with uplift, seismicity, and degassing and, on the longer-term, resurgence, suggesting repeated stalled intrusions. Finally, the expected advances in better understanding caldera unrest are discussed.

show abstract

Section: Types Of Caldera Unrestmentioning

confidence: 99%

Section: Types Of Caldera Unrestmentioning

confidence: 99%

An overview of recent (1988 to 2014) caldera unrest: Knowledge and perspectives

Acocella

Lorenzo

Newhall³

et al. 2015

Reviews of Geophysics

148

165

View full text Add to dashboard Cite

show abstract

“…The highest peak is located in the summit crater with an elevation of 707 m above sea level. Usu volcano has been in its active phase since the 1663 eruption, followed by nine eruptions including recent ones in 1910, 1943–1945, 1977–1982, and 2000 (Aoyama et al, ; Yokoyama et al, ; Yokoyama & Seino, ). Three summits Ko‐Usu (KU), O‐Usu (OU), and Usu‐Shinzan (US) in the summit crater (Figure ) were formed by the 1663, 1853, and 1977–1982 eruptions, respectively.…”

Section: Usu Volcanomentioning

confidence: 99%

“…Seismic activity continued during the whole period of unrest. For example, the 1977–1982 eruption accompanied thousands of earthquakes with magnitude up to 4 with a formation of a U‐shape normal fault in the summit crater (Aoyama et al, ; Okada et al, ). Second, all the eruptions generated remarkable ground deformation with an eventual formation of cryptodomes.…”

Section: Usu Volcanomentioning

confidence: 99%

See 1 more Smart Citation

Posteruptive Thermoelastic Deflation of Intruded Magma in Usu Volcano, Japan, 1992–2017

Wang

Aoki

2019

JGR Solid Earth

View full text Add to dashboard Cite

Secular ground subsidence at Usu volcano (Japan) has been reported around the eruption vents following the four eruptions in 1910, 1943, 1977, and 2000. However, the mechanisms accounting for the subsidence have not been well understood. In this study, we systematically investigated the posteruptive deformation at Usu volcano using interferometric synthetic aperture radar based on 111 JERS, ALOS-1, and ALOS-2 images acquired from 1992 to 2017. We also calculated quasi east-west and vertical ground displacements between 2006 and 2017. Our results show three localized deformation regions from west to east of Usu volcano with their locations corresponding to the 2000, 1977, and 1943 eruption vents, respectively. All the deformation sites show patterns of east-west contraction and subsidence. The extent and rate of posteruptive subsidence declined dramatically at the vent of the 2000 eruption site from 2006 to 2017, decreased gradually at the 1977 vent, and show a steady pattern for the 1943 site during 1992-2017. We ascribed the observed posteruptive subsidence to thermoelastic contraction of a sphere intruded at the time of the eruptions to constrain locations, depths, and volumes of heat sources with the assumption of the spherical source shapes. Thermoelastic modeling reveals that the heat sources are embedded at shallow depths not deeper than 400 m below sea level with volumes of about (8.72 ± 0.19) × 10 6 , (132.18 ± 5.21) × 10 6 , and (49.51 ± 2.02) × 10 6 m 3 for the 2000, 1977, and 1943 eruption sites, respectively. The modeling also highlights the importance of underground water in assessing the thermal diffusion process and the associated posteruptive deformation.

show abstract