Magma reservoir beneath Azumayama Volcano, NE Japan, as inferred from a three-dimensional electrical resistivity model explored by means of magnetotelluric method
Abstract An electrical resistivity model beneath Azumayama Volcano, NE Japan, is explored using magnetotelluric method to probe the magma/hydrothermal fluid distribution. Azumayama is one of the most concerning active volcanoes capable of producing a potential eruption triggered by the 2011 Tohoku-O...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
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SpringerOpen
2021-07-01
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| Series: | Earth, Planets and Space |
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| Online Access: | https://doi.org/10.1186/s40623-021-01451-y |
| _version_ | 1819128922974978048 |
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| author | Masahiro Ichiki Toshiki Kaida Takashi Nakayama Satoshi Miura Mare Yamamoto Yuichi Morita Makoto Uyeshima |
| author_facet | Masahiro Ichiki Toshiki Kaida Takashi Nakayama Satoshi Miura Mare Yamamoto Yuichi Morita Makoto Uyeshima |
| author_sort | Masahiro Ichiki |
| collection | DOAJ |
| description | Abstract An electrical resistivity model beneath Azumayama Volcano, NE Japan, is explored using magnetotelluric method to probe the magma/hydrothermal fluid distribution. Azumayama is one of the most concerning active volcanoes capable of producing a potential eruption triggered by the 2011 Tohoku-Oki Earthquake. The three-dimensional resistivity model reveals a conductive magma reservoir (< 3 Ωm) at depths of 3–15 km below sea level (bsl). The 67% and 90% confidence intervals of resistivity are 0.2–5 Ωm and 0.02–70 Ωm, respectively, for the magma reservoir. We assumed dacitic melt + rock at a shallow depth of 4 km bsl and andesitic melt + rock at a greater depth of 9 km bsl. The confidence interval of resistivity cannot be explained by using dacitic melt + rock condition at a depth of 4 km bsl. This suggests that very conductive hydrothermal fluids coexist with dacitic melt and rock in the shallow part of the magma reservoir. For the depth of 9 km bsl, the 67% confidence interval of resistivity is interpreted as water-saturated (8.0 weight %) andesitic melt–mafic rock complex with melt volume fractions greater than 4 volume %, while the shear wave velocity requires the fluid and/or melt volume fraction of 6–7 volume % at that depth. Considering the fluid and/or melt volume fraction of 6–7 volume %, the conductive hydrous phase is likewise required to explain the wide range of the 67% confidence interval of resistivity. The Mogi inflation source determined from geodetic data lies on the resistive side near the top boundary of the conductive magma reservoir at a depth of 2.7 or 3.7 km bsl. Assuming that the resistivity of the inflation source region is above the upper bound of the confidence interval of resistivity for the conductive magma reservoir and that the source region is composed of hydrothermal fluid + rock, the resistivity of the source region is explained by a hydrothermal fluid volume fraction below 5 volume %, which is the percolation threshold porosity in an effusive eruption. This indicates that the percolation threshold characterizes the inflation source region. |
| first_indexed | 2024-12-22T08:35:32Z |
| format | Article |
| id | doaj.art-8de65e1f9d27459497ec28064a27323f |
| institution | Directory Open Access Journal |
| issn | 1880-5981 |
| language | English |
| last_indexed | 2024-12-22T08:35:32Z |
| publishDate | 2021-07-01 |
| publisher | SpringerOpen |
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| series | Earth, Planets and Space |
| spelling | doaj.art-8de65e1f9d27459497ec28064a27323f2022-12-21T18:32:22ZengSpringerOpenEarth, Planets and Space1880-59812021-07-0173113010.1186/s40623-021-01451-yMagma reservoir beneath Azumayama Volcano, NE Japan, as inferred from a three-dimensional electrical resistivity model explored by means of magnetotelluric methodMasahiro Ichiki0Toshiki Kaida1Takashi Nakayama2Satoshi Miura3Mare Yamamoto4Yuichi Morita5Makoto Uyeshima6Research Center for Prediction of Earthquakes and Volcanic Eruptions, Graduate School of Science, Tohoku UniversityResearch Center for Prediction of Earthquakes and Volcanic Eruptions, Graduate School of Science, Tohoku UniversityResearch Center for Prediction of Earthquakes and Volcanic Eruptions, Graduate School of Science, Tohoku UniversityResearch Center for Prediction of Earthquakes and Volcanic Eruptions, Graduate School of Science, Tohoku UniversityResearch Center for Prediction of Earthquakes and Volcanic Eruptions, Graduate School of Science, Tohoku UniversityEarthquake Research Institute, The University of TokyoEarthquake Research Institute, The University of TokyoAbstract An electrical resistivity model beneath Azumayama Volcano, NE Japan, is explored using magnetotelluric method to probe the magma/hydrothermal fluid distribution. Azumayama is one of the most concerning active volcanoes capable of producing a potential eruption triggered by the 2011 Tohoku-Oki Earthquake. The three-dimensional resistivity model reveals a conductive magma reservoir (< 3 Ωm) at depths of 3–15 km below sea level (bsl). The 67% and 90% confidence intervals of resistivity are 0.2–5 Ωm and 0.02–70 Ωm, respectively, for the magma reservoir. We assumed dacitic melt + rock at a shallow depth of 4 km bsl and andesitic melt + rock at a greater depth of 9 km bsl. The confidence interval of resistivity cannot be explained by using dacitic melt + rock condition at a depth of 4 km bsl. This suggests that very conductive hydrothermal fluids coexist with dacitic melt and rock in the shallow part of the magma reservoir. For the depth of 9 km bsl, the 67% confidence interval of resistivity is interpreted as water-saturated (8.0 weight %) andesitic melt–mafic rock complex with melt volume fractions greater than 4 volume %, while the shear wave velocity requires the fluid and/or melt volume fraction of 6–7 volume % at that depth. Considering the fluid and/or melt volume fraction of 6–7 volume %, the conductive hydrous phase is likewise required to explain the wide range of the 67% confidence interval of resistivity. The Mogi inflation source determined from geodetic data lies on the resistive side near the top boundary of the conductive magma reservoir at a depth of 2.7 or 3.7 km bsl. Assuming that the resistivity of the inflation source region is above the upper bound of the confidence interval of resistivity for the conductive magma reservoir and that the source region is composed of hydrothermal fluid + rock, the resistivity of the source region is explained by a hydrothermal fluid volume fraction below 5 volume %, which is the percolation threshold porosity in an effusive eruption. This indicates that the percolation threshold characterizes the inflation source region.https://doi.org/10.1186/s40623-021-01451-yMagnetotelluricsElectrical resistivityShear wave velocityMagma reservoirMelt fractionPermeability |
| spellingShingle | Masahiro Ichiki Toshiki Kaida Takashi Nakayama Satoshi Miura Mare Yamamoto Yuichi Morita Makoto Uyeshima Magma reservoir beneath Azumayama Volcano, NE Japan, as inferred from a three-dimensional electrical resistivity model explored by means of magnetotelluric method Earth, Planets and Space Magnetotellurics Electrical resistivity Shear wave velocity Magma reservoir Melt fraction Permeability |
| title | Magma reservoir beneath Azumayama Volcano, NE Japan, as inferred from a three-dimensional electrical resistivity model explored by means of magnetotelluric method |
| title_full | Magma reservoir beneath Azumayama Volcano, NE Japan, as inferred from a three-dimensional electrical resistivity model explored by means of magnetotelluric method |
| title_fullStr | Magma reservoir beneath Azumayama Volcano, NE Japan, as inferred from a three-dimensional electrical resistivity model explored by means of magnetotelluric method |
| title_full_unstemmed | Magma reservoir beneath Azumayama Volcano, NE Japan, as inferred from a three-dimensional electrical resistivity model explored by means of magnetotelluric method |
| title_short | Magma reservoir beneath Azumayama Volcano, NE Japan, as inferred from a three-dimensional electrical resistivity model explored by means of magnetotelluric method |
| title_sort | magma reservoir beneath azumayama volcano ne japan as inferred from a three dimensional electrical resistivity model explored by means of magnetotelluric method |
| topic | Magnetotellurics Electrical resistivity Shear wave velocity Magma reservoir Melt fraction Permeability |
| url | https://doi.org/10.1186/s40623-021-01451-y |
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