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.
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Last updated on Aug. 05, 2022