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RESEARCH ARTICLE

Aeromagnetic constraints on the subsurface structure of Usu Volcano, Hokkaido, Japan

Shigeo Okuma 1 2 Tadashi Nakatsuka 1 Yoshihiro Ishizuka 1
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- Author Affiliations

1 Geological Survey of Japan, AIST, AIST Tsukuba Central 7, Higashi 1-1-1, Tsukuba 305-8567, Japan.

2 Corresponding author. Email: s.okuma@aist.go.jp

Exploration Geophysics 45(1) 24-36 https://doi.org/10.1071/EG13041
Submitted: 30 April 2013  Accepted: 26 September 2013   Published: 19 November 2013

Abstract

Usu Volcano, Hokkaido, Japan consists mainly of dacitic volcanic rocks underlain by basaltic somma lava and Pliocene–Pleistocene andesitic volcanic rocks, and erupts every 20–30 years. The most recent eruption, in 2000, was the first since 1978. We conducted a helicopter-borne high-resolution aeromagnetic survey almost three months after the start of this eruption. We calculated magnetic anomalies on a smoothed observation surface using a reduction method, assuming equivalent anomalies below the actual observation surface. We conducted three-dimensional (3D) imaging of magnetic anomalies to constrain the subsurface structure. Our model indicates that there are magnetisation highs in the main edifice of Usu Volcano, which may reflect the subsurface distribution of the Usu somma lava. Meanwhile, magnetisation lows lie north-west of the Nishi-Yama Craters Area and on Higashi-Maruyama Cryptodome, where nearby Pliocene and Pleistocene volcanic rocks, respectively, are found. The reverse magnetisation observed at outcrops close to these sites could explain the magnetisation lows.

Although the survey improved our understanding of the surface and subsurface distribution of volcanic rocks in the edifice and basement of Usu Volcano, some limitations remain. No information about the magmas intruded during the recent eruptions in 1977–1978 and 2000 was obtained by the survey, though some of these intrusions were revealed by other geophysical data. The small magnetic contrast between the intruded magmas and their host rocks is the most probable reason. Perhaps the intruded magmas (in particular, those of the most recent eruption) had not cooled enough to become strongly magnetised by the time the survey was conducted.

Key words: aeromagnetic survey, lava, magnetic anomaly, Usu Volcano, volcanic rocks.


References

Blakely, R. J., 1995, Potential theory in gravity and magnetic applications: Cambridge University Press.

Geospatial Information Authority of Japan, 1999, Digital Map 50 m Grid (Elevation), NIPPON-I, CD-ROM.

Geospatial Information Authority of Japan, 2007, Digital Map 10 m Grid (Elevation of Active Volcanoes), CD-ROM.

Hashimoto, T., Hurst, T., Suzuki, A., Mogi, T., Yamaya, Y., and Tamura, M., 2008, The role of thermal viscous remanent magnetisation (TVRM) in magnetic changes associated with volcanic eruptions: insights from the 2000 eruption of Mt Usu, Japan: Journal of Volcanology and Geothermal Research, 176, 610–616
The role of thermal viscous remanent magnetisation (TVRM) in magnetic changes associated with volcanic eruptions: insights from the 2000 eruption of Mt Usu, Japan:Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD1cXhtFOksrnJ&md5=c4002da46c07f7e190d3e729663105c3CAS |

Hashimoto, T., Utsugi, M., Nakatsuka, T., Okuma, S., Koyama, T., and Kanda, W., 2011, Temporal magnetic changes possibly due to cooling magmas as revealed by repeat helicopter-borne surveys over an active volcano: Proceedings of the 10th SEGJ International Symposium, 276–279.10.1190/segj102011-001.68

Katsui, Y., Komuro, H., and Uda, T., 1985, Development of faults and growth of Usu-Shinzan Cryptodome in 1977–1982 at Usu Volcano, North Japan: Journal of the Faculty of Science, Hokkaido University, Series 4, Geology and Mineralogy, 21, 339–362

Matsushima, N., 2003, Mathematical simulation of magma-hydrothermal activity associated with the 1977 eruption of Usu volcano: Earth, Planets, and Space, 9, 559–568

Matsushima, N., 2010, Explanatory note of resistivity cross-section of Usu Volcano by magnetotelluric surveys, Integrated Geophysical Maps of Usu Volcano: Digital Geoscience Map P-7(CD), Geological Survey of Japan, AIST.

Matsushima, N., Oshima, H., Ogawa, Y., Takakura, S., Satoh, H., Utsugi, M., and Nishida, Y., 2001, Magma prospecting in Usu volcano, Hokkaido, Japan, using magnetotelluric soundings: Journal of Volcanology and Geothermal Research, 109, 263–277
Magma prospecting in Usu volcano, Hokkaido, Japan, using magnetotelluric soundings:Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD3MXnslWmt7Y%3D&md5=2a4720824c6ddd50779a2c80bb93b7c7CAS |

Maus, S., Macmillan, S., Chernova, T., Choi, S., Dater, D., Golovkov, V., Lesur, V., Lowes, F., Lühr, H., Mai, W., McLean, S., Olsen, N., Rother, M., Sabaka, T., Thomson, A., and Zvereva, T., 2005, The 10th-generation international geomagnetic reference field: Geophysical Journal International, 161, 561–565
The 10th-generation international geomagnetic reference field:Crossref | GoogleScholarGoogle Scholar |

Murakami, R., Ozawa, S., Nishimura, T., and Tada, T., 2001, A model of magma movements associated with the 2000 eruption of Usu volcano inferred by crustal deformation detected by continuous GPS and other geodetic measurements: Journal of the Geospatial Information Authority of Japan, 95, 99–105

Murase, T., 1962, Viscosity and related properties of volcanic rocks at 800°C to 1400°C: Journal of the Faculty of Science, Hokkaido University, Series 7, Geophysics, 1, 487–584

Nakatsuka, T., 1995, Minimum norm inversion of magnetic anomalies with application to aeromagnetic data in the Tanna area, Central Japan: Journal of Geomagnetism and Geoelectricity, 47, 295–311
Minimum norm inversion of magnetic anomalies with application to aeromagnetic data in the Tanna area, Central Japan:Crossref | GoogleScholarGoogle Scholar |

Nakatsuka, T., and Okuma, S., 2006a, Reduction of magnetic anomaly observations from helicopter surveys at varying elevations: Exploration Geophysics, 37, 121–128
Reduction of magnetic anomaly observations from helicopter surveys at varying elevations:Crossref | GoogleScholarGoogle Scholar |

Nakatsuka, T., and Okuma, S., 2006b, 3D subsurface imaging by aeromagnetic data: Proceedings of the 115th SEGJ Conference, 196–199.

Nakatsuka, T., and Okuma, S., 2006c, Crossover analysis for the aeromagnetic survey at varying elevations, and its application to extracting temporal magnetic anomaly change: Butsuri-Tansa (Geophysical Exploration), 59, 449–458
Crossover analysis for the aeromagnetic survey at varying elevations, and its application to extracting temporal magnetic anomaly change:Crossref | GoogleScholarGoogle Scholar |

Nakatsuka, T., and Okuma, S., 2009, Aeromagnetic 3D subsurface imaging with source volume minimization: Proceedings of the 9th SEGJ International Symposium, 6 (4pp), CD-ROM. 10.1190/segj092009-001.2

Nakatsuka, T., Okuma, S., and Joint Group for Usu Volcano Airborne Magnetic Survey, 2011, Magnetic anomaly change of Usu Volcano 2000–2010 detected by repeated aeromagnetic surveys with a study on the accuracy of 2000 survey altitude data: Proceedings of the 2011 Conductivity Anomaly Research Group Meeting, 37–44.

Nemoto, S., Hayakawa, M., Takahashi, K., and Koana, S., 1957, Report on the geological, geophysical and geochemical studies of Usu Volcano (Showa-Shinzan): Report of the Geological Survey of Japan, 170, 149p+24p [English abstract].

Nishida, Y., and Miyajima, E., 1984, Subsurface structure of Usu Volcano, Japan, as revealed by detailed magnetic survey: Journal of Volcanology and Geothermal Research, 22, 271–285
Subsurface structure of Usu Volcano, Japan, as revealed by detailed magnetic survey:Crossref | GoogleScholarGoogle Scholar |

Ohta, R., 1956, Geological map of Japan 1 : 50,000, Abuta: Geological Survey of Japan.

Okuma, S., Morijiri, R., Makino, M., and Nakatsuka, T., 1995, Evaluation of a high-resolution aeromagnetic survey in a volcanic region – The case of Yurihara area, northeast Japan: Butsuri-Tansa (Geophysical Exploration), 48, 316–332

Okuma, S., Nakatsuka, T., Morijiri, R., Makino, M., Uchida, T., Ogawa, Y., Takakura, S., and Matsushima, N., 2001, Preliminary results of a high-resolution aeromagnetic survey over Usu Volcano, Hokkaido, Japan: Bulletin of the Geological Survey of Japan, 52, 149–154

Okuma, S., Nakatsuka, T., Takakura, S., and Morijiri, R., 2002, Helicopter-borne EM survey over Usu Volcano, Hokkaido, Japan, with a special reference to the Usu 2000 eruption: Bulletin of the Volcanological Society of Japan, 47, 533–546

Okuma, S., Nakatsuka, T., Morijiri, R., and Makino, M., 2003, High-resolution aeromagnetic anomaly map of Usu Volcano: Total intensity aeromagnetic maps, 41, Geological Survey of Japan, AIST.

Okuma, S., Nakatsuka, T., Komazawa, M., Sugihara, M., Nakano, S., Furukawa, R., and Supper, R., 2006, Shallow subsurface structure of the Vulcano-Lipari volcanic complex, Italy, constrained by helicopter-borne aeromagnetic surveys: Exploration Geophysics, 37, 129–138
Shallow subsurface structure of the Vulcano-Lipari volcanic complex, Italy, constrained by helicopter-borne aeromagnetic surveys:Crossref | GoogleScholarGoogle Scholar |

Okuma, S., Nakatsuka, T., Komazawa, M., Matsushima, N., Satoh, H., Takakura, S., Ishizuka, Y., Onizawa, S., Ogawa, Y., and Mogi, T., 2010, Explanatory note of integrated geophysical maps of Usu Volcano, Integrated Geophysical Maps of Usu Volcano: Digital Geoscience Map P-7(CD), Geological Survey of Japan, AIST.

Onizawa, S., 2010, Explanatory note of precursory seismic activity of the Usu 2000 eruption, Integrated Geophysical Maps of Usu Volcano: Digital Geoscience Map P-7(CD), Geological Survey of Japan, AIST.

Oshima, H., and Matsushima, N., 1999, Preliminary report on hydrological environment in the shallow part of Usu Volcano: Geophysical Bulletin of Hokkaido University, 62, 79–97

Soya, T., Katsui, Y., Niida, K., Sakai, K., and Tomiya, A., 2007, Geological map of Usu Volcano (2nd edition): Geological Map of Volcanoes, 2, Geological Survey of Japan, AIST.

Yahata, M., 2002, Fragmentation depths and its temporal variation during Usu 2000 phreatomagmatic and phreatic eruptions: Bulletin of the Volcanological Society of Japan, 47, 263–278
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