[S-VC32] 活動的火山

[SVC32-04] Studying Active Volcanism with Joint Muon and Ground Surface Deformation Monitoring at Sakurajima Volcano

*Laszlo Olah^1,2、Gergő Hamar^1,2、Takao Ohminato³、Hiroyuki K.M. Tanaka^2,3、László Tercsi¹、Soshi Tsuno⁴、Dezső Varga^1,2 (1.HUN-REN Wigner Research Centre for Physics, Budapest, Hungary、2.International Virtual Muography Institute (VMI), Global、3.Earthquake Research Institute, The University of Tokyo, Tokyo, Japan、4.National Institute of Technology, Kagoshima College, Kagoshima, Japan)

キーワード：magma, degassing, cosmic-ray muon, ground deformation, multi-vent volcanoes

Muography is a passive and non-destructive geophysical imaging technique that is based on the measurement of cosmic-ray induced muon particles [1]. Muography allows the monitoring of mass changes that caused by subsurface volcanic phenomena via measurement of the yield of muons penetrated across the studied volcanic edifice, similarly how X-raying is applied for medical imaging. The University of Tokyo and HUN-REN Wigner Research Centre for Physics developed Sakurajima Muography Observatory (SMO) based on gaseous particle detectors for monitoring of mass changes inside the volcano and on the slopes of the volcanic edifice [2,3]. Since 2018, we conducted joint muon and ground deformation monitoring through active and dormant periods. The SMO revealed mass density increases in the upper conduits caused by the pressurization of magmatic materials and mass density decreases as a result of pressure releases by the occurrence of eruption sequences [4,5]. Muographic data explained the link between ground surface deformation of active craters and eruption frequences. A moderate inverse correlation has been found between the mass densities observed beneath the Minamidake and Showa craters (see in the Figure) that indicated a magmatic gas flux dynamics which characterizing branched conduits [6]. Muographic monitoring thus reveals the shallow magmatic processes during the switch of eruptive activity between the craters of multi-vent volcanoes. Muographic monitoring the in-conduit physical mechanism underlying the switching of eruptive activity between the craters of multi-vent volcanoes could contribute to hazard assessment at these complex edifices.

[1] Oláh, L., Tanaka, H. K. M., & Varga, D. (2022). Muography: Exploring Earth's subsurface with elementary particles. Geophysical Monograph Series, 270. https://doi.org/10.1002/9781119722748

[2] Oláh, L. et al. (2018) High-definition and low-noise muography of the Sakurajima volcano with gaseous tracking detectors. Sci Rep 8, 3207 https://doi.org/10.1038/s41598-018-21423-9

[3] Oláh, L., et al. (2021) Muographic monitoring of hydrogeomorphic changes induced by post-eruptive lahars and erosion of Sakurajima volcano. Sci Rep 11, 17729. https://doi.org/10.1038/s41598-021-96947-8

[4] Oláh, L., et al. (2019) Plug Formation Imaged Beneath the Active Craters of Sakurajima Volcano With Muography. Geophysical Research Letters, 46, 10417-10424. https://doi.org/10.1029/2019GL084784

[5] Oláh, L., et al. (2023) Muon Imaging of Volcanic Conduit Explains Link Between Eruption Frequency and Ground Deformation. Geophysical Research Letters, 50, e2022GL101170. https://doi.org/10.1029/2022GL101170

[6] Oláh, L., et al. (2024) Branched Conduit Structure Beneath the Active Craters of Sakurajima Volcano Inferred From Muography, Journal of Geophysical Research: Solid Earth, 129, e2023JB028514. https://doi.org/10.1029/2023JB028514