[S-VC31] 活動的火山

[SVC31-P06] 2022年9月に実施された立山火山地獄谷における水準測量

*堀田 耕平¹、瀧 大輝¹、前田 知秀¹ (1.富山大学)

キーワード：弥陀ヶ原火山、立山火山、水準測量、地殻変動、富山、飛騨山脈

Leveling surveys have been conducted in Jigokudani valley, Tateyama volcano, since 2015. Benchmarks, which were set along the walkway of the valley, showed subsidence up to 5.6 cm during the four-year period from September 2016 to September 2020. Subsidence started in 2017–2018 when a new crater was formed at the southwestern area of the valley (Hotta et al., 2022). During the period from September 2020 to September 2021, ground of the valley was revealed to have re-uplifted up to 0.8 cm probably due to accumulation of volcanic gas or fluid (Hotta et al., under revision). Leveling survey conducted in September 2022 revealed that uplift has continued in the central area of the valley during the following one-year period from September 2021 to September 2022. Maximum uplift was found to be 0.9 cm. The southwestern area of the valley near the new crater formed in 2017–2018, however, showed subsidence up to 0.8 cm. It is considered that volcanic gas or fluid have been accumulated beneath the central area of the valley similarly to the previous one-year period. Besides, volcanic gas or fluid beneath the southwestern area of the valley have been emitted from the surface due to violent fumarolic activities.
This study was supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan, under its Earthquake and Volcano Hazards Observation and Research Program.