[S-CG56] Crustal fluids and deformation

[SCG56-02] Continuous Monitoring of Radon in Hot Spring Water at the Eastern Margin of the Aira Caldera – Development of the Observation System and Preliminary Data Analysis –

*Kuniyo Kawabata¹, Fumiaki Tsunomori³, Yujin Kitamura² (1.Center for General Education, Institute for Comprehensive Education, KAGOSHIMA UNIVERSITY, 2.Headquarters for Campus Educational System Reform Center for Institutional Research, Educational Development, and Learning Support, Ochanomizu University, 3.Geochemical Research Center, Geochemical Research Center, Graduate School of Science, THE UNIVERSITY OF TOKYO)

Keywords:Radon gas monitoring, Aira Caldera, Hot spring

Our research aims to understand geophysical phenomena associated with crustal deformation from a geochemical perspective, with a particular focus on the continuous monitoring of radon concentration variations in groundwater and crustal fluids. Investigations conducted on hot spring waters around the Aira Caldera in Kagoshima Prefecture have identified hot springs with distinctive characteristics, such as high helium isotope ratios, evidence of magmatic water mixing, and elevated radon concentrations. The distribution of these hot springs is regulated by geological structures, indicating a strong relationship between geological features and hot spring distribution.

Radon concentration analyses (²²²Rn) in groundwater have revealed region-specific variations across different hot springs. Radon concentrations are known to fluctuate due to processes such as rock fracturing, making them potential indicators of crustal deformation. This study reports on the development of a continuous radon monitoring system and presents observational results of radon concentrations from hot springs located along the eastern margin of the Aira Caldera.