Anatomy of active volcanic edifice at the Kusatsu–Shirane volcano, Japan, by magnetotellurics: hydrothermal implications for volcanic unrests
Abstract We aimed to perform three-dimensional imaging of the underlying geothermal system to a depth of 2 km using magnetotellurics (MT) at around the Yugama crater, the Kusatsu–Shirane Volcano, Japan, which is known to have frequent phreatic eruptions. We deployed 91 MT sites focusing around the p...
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| Format: | Article |
| Language: | English |
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SpringerOpen
2020-10-01
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| Series: | Earth, Planets and Space |
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| Online Access: | http://link.springer.com/article/10.1186/s40623-020-01283-2 |
| _version_ | 1811225854078877696 |
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| author | Kuo Hsuan Tseng Yasuo Ogawa Nurhasan Sabri Bülent Tank Naoto Ujihara Yoshimori Honkura Akihiko Terada Yoshiya Usui Wataru Kanda |
| author_facet | Kuo Hsuan Tseng Yasuo Ogawa Nurhasan Sabri Bülent Tank Naoto Ujihara Yoshimori Honkura Akihiko Terada Yoshiya Usui Wataru Kanda |
| author_sort | Kuo Hsuan Tseng |
| collection | DOAJ |
| description | Abstract We aimed to perform three-dimensional imaging of the underlying geothermal system to a depth of 2 km using magnetotellurics (MT) at around the Yugama crater, the Kusatsu–Shirane Volcano, Japan, which is known to have frequent phreatic eruptions. We deployed 91 MT sites focusing around the peak area of 2 km × 2 km with typical spacings of 200 m. The full tensor impedances and the magnetic transfer functions were inverted, using an unstructured tetrahedral finite element code to include the topographic effect. The final model showed (1) low-permeability bell-shaped clay cap (C1) as the near-surface conductor, (2) brine reservoir as a deep conductor (C3) at a depth of 1.5 km from the surface, and (3) a vertical conductor (C2) connecting the deep conductor to the clay cap which implies an established fluid path. The columnar high-seismicity distribution to the east of the C2 conductor implies that the flushed vapor and magmatic gas was released from the brine reservoir by breaking the silica cap at the brittle–ductile transition. The past magnetization/demagnetization sources and the inflation source of the 2014 unrest are located just below the clay cap, consistent with the clay capped geothermal model underlain by brine reservoir. The resistivity model showed the architecture of the magmatic–hydrothermal system, which can explain the episodic volcanic unrest. |
| first_indexed | 2024-04-12T09:14:12Z |
| format | Article |
| id | doaj.art-c62ea17006904237b7cb39c183e7ef20 |
| institution | Directory Open Access Journal |
| issn | 1880-5981 |
| language | English |
| last_indexed | 2024-04-12T09:14:12Z |
| publishDate | 2020-10-01 |
| publisher | SpringerOpen |
| record_format | Article |
| series | Earth, Planets and Space |
| spelling | doaj.art-c62ea17006904237b7cb39c183e7ef202022-12-22T03:38:54ZengSpringerOpenEarth, Planets and Space1880-59812020-10-0172111110.1186/s40623-020-01283-2Anatomy of active volcanic edifice at the Kusatsu–Shirane volcano, Japan, by magnetotellurics: hydrothermal implications for volcanic unrestsKuo Hsuan Tseng0Yasuo Ogawa1Nurhasan2Sabri Bülent Tank3Naoto Ujihara4Yoshimori Honkura5Akihiko Terada6Yoshiya Usui7Wataru Kanda8Department of Earth and Planetary Sciences, Tokyo Institute of TechnologyVolcanic Fluid Research Center, Tokyo Institute of TechnologyDepartment of Earth and Planetary Sciences, Tokyo Institute of TechnologyDepartment of Earth and Planetary Sciences, Tokyo Institute of TechnologyDepartment of Earth and Planetary Sciences, Tokyo Institute of TechnologyVolcanic Fluid Research Center, Tokyo Institute of TechnologyVolcanic Fluid Research Center, Tokyo Institute of TechnologyDepartment of Earth and Planetary Sciences, Tokyo Institute of TechnologyVolcanic Fluid Research Center, Tokyo Institute of TechnologyAbstract We aimed to perform three-dimensional imaging of the underlying geothermal system to a depth of 2 km using magnetotellurics (MT) at around the Yugama crater, the Kusatsu–Shirane Volcano, Japan, which is known to have frequent phreatic eruptions. We deployed 91 MT sites focusing around the peak area of 2 km × 2 km with typical spacings of 200 m. The full tensor impedances and the magnetic transfer functions were inverted, using an unstructured tetrahedral finite element code to include the topographic effect. The final model showed (1) low-permeability bell-shaped clay cap (C1) as the near-surface conductor, (2) brine reservoir as a deep conductor (C3) at a depth of 1.5 km from the surface, and (3) a vertical conductor (C2) connecting the deep conductor to the clay cap which implies an established fluid path. The columnar high-seismicity distribution to the east of the C2 conductor implies that the flushed vapor and magmatic gas was released from the brine reservoir by breaking the silica cap at the brittle–ductile transition. The past magnetization/demagnetization sources and the inflation source of the 2014 unrest are located just below the clay cap, consistent with the clay capped geothermal model underlain by brine reservoir. The resistivity model showed the architecture of the magmatic–hydrothermal system, which can explain the episodic volcanic unrest.http://link.springer.com/article/10.1186/s40623-020-01283-2Phreatic eruptionMagnetotelluric methodClay capBrineUnrest |
| spellingShingle | Kuo Hsuan Tseng Yasuo Ogawa Nurhasan Sabri Bülent Tank Naoto Ujihara Yoshimori Honkura Akihiko Terada Yoshiya Usui Wataru Kanda Anatomy of active volcanic edifice at the Kusatsu–Shirane volcano, Japan, by magnetotellurics: hydrothermal implications for volcanic unrests Earth, Planets and Space Phreatic eruption Magnetotelluric method Clay cap Brine Unrest |
| title | Anatomy of active volcanic edifice at the Kusatsu–Shirane volcano, Japan, by magnetotellurics: hydrothermal implications for volcanic unrests |
| title_full | Anatomy of active volcanic edifice at the Kusatsu–Shirane volcano, Japan, by magnetotellurics: hydrothermal implications for volcanic unrests |
| title_fullStr | Anatomy of active volcanic edifice at the Kusatsu–Shirane volcano, Japan, by magnetotellurics: hydrothermal implications for volcanic unrests |
| title_full_unstemmed | Anatomy of active volcanic edifice at the Kusatsu–Shirane volcano, Japan, by magnetotellurics: hydrothermal implications for volcanic unrests |
| title_short | Anatomy of active volcanic edifice at the Kusatsu–Shirane volcano, Japan, by magnetotellurics: hydrothermal implications for volcanic unrests |
| title_sort | anatomy of active volcanic edifice at the kusatsu shirane volcano japan by magnetotellurics hydrothermal implications for volcanic unrests |
| topic | Phreatic eruption Magnetotelluric method Clay cap Brine Unrest |
| url | http://link.springer.com/article/10.1186/s40623-020-01283-2 |
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