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Examination of the causes of geomagnetic changes observed during periods of volcanic unrest based on numerical modeling

Wataru Kanda 1; Shunki Tamura2,3

  • Affiliations: 1Institute of Integrated Research, Institute of Science Tokyo, Tokyo, Japan; 2School of Science, Tokyo Institute of Technology, Tokyo Japan; 3Unito Inc., Tokyo, Japan

  • Presentation type: Poster

  • Presentation time: Monday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 270

  • Programme No: 2.4.42

  • Theme 2 > Session 4

Abstract

Geomagnetic observations around the active craters of volcanoes provide information on the thermal conditions underground, which is extremely useful for understanding volcanic activity. This aims to measure changes in the magnetization structure inside the volcanic edifice caused by heat supply from the deep as geomagnetic changes. However, when continuous observations are performed, there are cases where the geomagnetic changes remain unchanged even though other mechanical observations indicate increased activity or are observed at a different time from the increased activity. For example, at Kusatsu-Shirane Volcano, ground deformation suggesting the inflation of the underground was continuously monitored in association with increased seismic activity from March 2014. Still, geomagnetic changes were only observed for a short period in May 2014. In this study, we numerically examined this difference in the timing of activity from the perspective of changes in the magnetization structure around the assumed source of ground deformation. As a result, it was found that in volcanoes composed of weakly magnetized andesitic rocks such as Kusatsu-Shirane Volcano, even if thermal demagnetization occurs, no changes can be observed depending on the depth at which it occurs, and that the speed of change differs depending on whether demagnetization is caused by thermal conduction of the rocks or advective heat transfer due to high-temperature fluids.