[S-GD03] 地殻変動

[SGD03-07] Decadal Ground Deformation of Ontake Volcano: Insights from InSAR Time-Series Analysis

*AGUSTAN AGUSTAN^1,2、Takeo ITO¹、Arif Aditiya¹ (1.Earthquake and Volcano Research Center - Nagoya University 、2.Research Center for Area Studies, National Research and Innovation Agency (BRIN), Indonesia)

キーワード：Ontake Volcano, time-series InSAR, long term, ground deformation

Satellite-based remote sensing plays a crucial role in monitoring ground deformation at active volcanoes, offering valuable insights into long-term surface dynamics. The Copernicus Sentinel-1 mission, equipped with C-band Synthetic Aperture Radar (SAR), enables continuous observation of volcanic deformation through Interferometric Synthetic Aperture Radar (InSAR) techniques. In this study, we analyze a decade of Sentinel-1 interferogram pairs acquired from the Alaska Satellite Facility’s Hybrid Pluggable Processing Pipeline (HyP3) to investigate ground displacement at Ontake Volcano from November 2014 to January 2025 using InSAR time-series analysis with the MintPy framework. Ontake Volcano, Japan’s second-highest active stratovolcano, has exhibited significant ground deformation following its unexpected phreatic eruption in 2014. To ensure robust deformation detection, we applied orbital, topographic, and atmospheric corrections, utilizing the Copernicus GLO-30 DEM and ERA5 reanalysis data for topographic and phase delay mitigation. Additionally, a spatio-temporal filtering approach was implemented to reduce residual noise in time-series deformation products, enhancing measurement accuracy. Our results reveal a predominant subsidence trend exceeding 40 cm at key locations, indicating sustained deflation within the volcanic system. A marked acceleration in subsidence was observed between 2020 and 2021, suggesting dynamic shifts in magmatic or hydrothermal pressure. Post-2022 data indicate a stabilization phase, with minor fluctuations likely associated with continued fluid migration. These findings highlight the importance of integrating InSAR-based remote sensing techniques for continuous volcano monitoring. The observed deformation patterns provide crucial insights into Ontake’s subsurface processes and potential hazards. Long-term InSAR analysis enhances early warning systems by detecting subtle but significant ground deformation changes, reinforcing the necessity of sustained geodetic monitoring in active volcanic regions.