JDR Vol.17 No.5 pp. 630-638
doi: 10.20965/jdr.2022.p0630


Post-Eruptive Persistent Cooling Beneath the Summit Crater of Usu Volcano as Revealed by Magnetic Repeat Surveys

Takeshi Hashimoto

Institute of Seismology and Volcanology, Faculty of Science, Hokkaido University
Kita-10 Nishi-8, Kita-ku, Sapporo, Hokkaido 060-0810, Japan

Corresponding author

December 26, 2021
June 16, 2022
August 1, 2022
geomagnetism, total field, remagnetization, cooling, Usu Volcano

Remarkable and continuous geomagnetic field change, suggesting remagnetization at a shallow depth, was detected through repeated geomagnetic field observation of the summit area of Mt. Usu Volcano from 2008 to 2021. Long-term cooling of the remnant magma, that intruded during the 1977–82 eruption, was considered responsible for the remagnetization. A magnetic dipole parallel to the present geomagnetic field well reproduced the observation. The modeled source was located near the Ginnuma crater on the south side of the previously inferred intrusive body beneath the Usu-Shinzan cryptodome. Meanwhile, no magnetic source was detected on the other side of the intrusion, implying asymmetric heat transport paths around the intrusion. Considering previous studies on seismicity, geodetic modeling, and resistivity structure, the magnetic source region is plausibly a high permeability zone through which heat from the intruded magma has been efficiently transported. In other words, the source region can be a key monitoring target for future eruptions as it may be linked to the subsurface magma system.

Cite this article as:
T. Hashimoto, “Post-Eruptive Persistent Cooling Beneath the Summit Crater of Usu Volcano as Revealed by Magnetic Repeat Surveys,” J. Disaster Res., Vol.17 No.5, pp. 630-638, 2022.
Data files:
  1. [1] Y. Tanaka, “Eruption mechanism as inferred from geomagnetic changes with special attention to the 1989–1990 activity of Aso Volcano,” J. Volcanol. Geotherm. Res., Vol.56, No.3, pp. 319-338, 1993.
  2. [2] R. J. Mueller, M. J. S. Johnston, and J. O. Langbein, “Possible tectonomagnetic effect observed from mid-1989, to mid-1990, in Long Valley Caldera, California,” Geophys. Res. Lett., Vol.18, No.4, pp. 601-604, 1991.
  3. [3] J. Zlotnicki, J. L. Le Mouël, J. C. Delmond, C. Pambrun, and H. Delorme, “Magnetic variations on Piton de la Fournaise volcano. Volcanomagnetic signals associated with the November 6 and 30, 1987, eruptions,” J. Volcanol. Geotherm. Res., Vol.56, No.3, pp. 281-296, 1993.
  4. [4] T. Hashimoto, M. Utsugi, T. Ohkura, W. Kanda, A. Terada, S. Miura, and M. Iguchi, “On the source characteristics of demagnetization and ground deformation associated with non-magmatic activity,” Bull. Volcanol. Soc. Japan, Vol.64, No.2, pp. 103-119, 2019 (in Japanese).
  5. [5] W. Kanda, M. Utsugi, Y. Tanaka, T. Hashimoto, I. Fujii, T. Hasenaka, and N. Shigeno, “A heating process of Kuchi-erabu-jima volcano, Japan, as inferred from geomagnetic field variations and electrical structure,” J. Volcanol. Geotherm. Res., Vol.189, Nos.1-2, pp. 158-171, 2010.
  6. [6] T. Hashimoto, M. Utsugi, S. Sakanaka, and Y. Tanaka, “Heat Discharging Process and Geomagnetic changes of Iwoyama, Kuju Volcano,” Annuals of Disas. Prev. Res. Inst., Kyoto Univ., No.45B-1, pp. 617-625, 2002 (in Japanese).
  7. [7] T. Yamamoto, A. Takagi, K. Fukui, and T. Owada, “Hydrothermal Activity Inferred from Comprehensive Observation of Unrest in Adatara Volcano,” Papers Meteorol. Geophys., Vol.59, pp. 39-64, 2008 (in Japanese).
  8. [8] K. Takahashi and I. Fujii, “Long-term thermal activity revealed by magnetic measurements at Kusatsu-Shirane volcano, Japan,” J. Volcanol. Geotherm. Res., Vol.285, pp. 180-194, 2014.
  9. [9] T. Hashimoto, T. Hurst, A. Suzuki, T. Mogi, Y. Yamaya, and M. Tamura, “The role of thermal viscous remanent magnetisation (TVRM) in magnetic changes associated with volcanic eruptions: Insights from the 2000 eruption of Mt Usu, Japan,” J. Volcanol. Geotherm. Res., Vol.176, pp. 610-616, 2008.
  10. [10] T. Soya, Y. Katsui, K. Niida, K. Sakai, and A. Tomiya, “Geological Map of Usu Volcano (2nd Ed.),” Geological Survey of Japan, AIST, 2007.
  11. [11] Japan Meteorological Agency and Volcanological Society of Japan (Eds.), “National catalogue of the active volcanoes in Japan (4th Ed.),” 2013, [accessed June 16, 2022]
  12. [12] H. Aoyama, S. Onizawa, T. Kobayashi, T. Tameguri, T. Hashimoto, H. Oshima, and H. Y. Mori, “Inter-eruptive volcanism at Usu volcano: Micro-earthquakes and dome subsidence,” J. Volcanol. Geotherm. Res., Vol.187, Nos.3-4, pp. 203-217, 2009.
  13. [13] X. Wang and Y. Aoki, “Posteruptive thermoelastic deflation of intruded magma in Usu volcano, Japan, 1992–2017,” J. Geophys. Res. Solid Earth, Vol.124, No.1, pp. 335-357, 2019.
  14. [14] [accessed June 16, 2022]
  15. [15] S. Onizawa, H. Oshima, H. Aoyama, H. Y. Mori, T. Maekawa, A. Suzuki, T. Tsutsui, N. Matsuwo, J. Oikawa, T. Ohminato, K. Yamamoto, T. Mori, T. Taira, H. Miyamachi, and H. Okada, “P-wave velocity structure of Usu volcano: Implication of structural controls on magma movements and eruption locations,” J. Volcanol. Geotherm. Res., Vol.160, Nos.1-2, pp. 175-194, 2007.
  16. [16] Japan Meteorological Agency, “15. Usuzan,” Japan Meteorological Agency and Volcanological Society of Japan (Eds.), “National catalogue of the active volcanoes in Japan (4th Ed.),” 2013, [accessed June 16, 2022]
  17. [17] S. Okuma, T. Nakatsuka, S. Takakura, and R. Morijiri, “Helicopter-borne EM survey over Usu Volcano, Hokkaido Japan, with a special attention to the Usu 2000 eruption,” Bull. Volcanol. Soc. Japan, Vol.47, No.5, pp. 533-546, 2002 (in Japanese).
  18. [18] Y. Sasai, “Tectonomagnetic modeling on the basis of the linear piezomagnetic effect,” Bull. Earthq. Res. Inst. Univ. Tokyo, Vol.66, pp. 585-722, 1991.
  19. [19] N. Matsushima, “Mathematical simulation of magma-hydrothermal activity associated with the 1977 eruption of Usu volcano,” Earth Planets Space, Vol.55, No.9, pp. 559-568, 2003.
  20. [20] P. A. Hernández, K. Notsu, J. M. Salazar, T. Mori, G. Natale, H. Okada, G. Virgili, Y. Shimoike, M. Sato, and N. M. Pérez, “Carbon Dioxide Degassing by Advective Flow from Usu Volcano, Japan,” Science, Vol.292, No.5514, pp. 83-86, 2001.
  21. [21] Japan Volcanological Data Network, [accessed June 16, 2022]

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