5:15 PM - 7:15 PM
[SGD03-P02] Ground deformation on Hachimantai and Iwate volcano in 2020-2024 detected by GNSS and SAR data
Keywords:Ground deformation, GNSS, SAR, Volcano, Hachimantai, Iwate volcano
Hachimantai and Iwate volcanoes are andesitic volcanoes located on the border of Akita and Iwate prefectures in the Tohoku region of Japan. Iwate volcano has experienced an unrest episode accompanied by inflation and M6.1 earthquake in 1998. This study aims to explore the spatiotemporal evolution of ground deformation in Hachimantai and Iwate volcanoes and to investigate the geometry of the pressure source of Hachimantai and Iwate volcanoes. We used GNSS (GEONET, JMA and V-net) and SAR (ALOS-2/PALSAR-2) data collected in 2015–2024 to investigate the spatio-temporal characteristics of ground deformation. To isolate the volcanic deformation at the Hachimantai and Iwate volcano, the long-wavelength deformation was corrected by modeling as a high-degree polynomial planar using GNSS data acquired away from the volcanic area. For the SAR data, the long-wavelength signals in SAR data were also corrected by modeling them as polynomial planar after the ionospheric correction.
The GNSS data revealed that the inflation at Hachimantai volcano started in early 2020 with a constant inflation rate. The result also showed the broader inflation signals on Iwate volcano since the beginning of 2024. The inflation on both volcanoes is still growing at the end of 2024. ALOS-2/PALSAR-2 InSAR revealed that the line-of-sight (LOS) shortening, indicating inflation, was located at the center of Hachimantai volcano during 2020-2023, while another LOS shortening signal was also detected on the western part of Iwate volcano since early 2024.
We derived the best-fit geometry for the pressure sources driving the detected inflation to discuss the subsurface volcanic system of the Hachimantai and Iwate volcanoes. The best-fit parameters were optimized using the Markov chain Monte Carlo approach. The best-fit geometry of the pressure source on the Hachimantai volcano was inferred from GNSS and SAR data in 2020–2023, and that of the Iwate volcano was inferred from GNSS and SAR data in 2024. The best-fit geometry of the pressure source at Hachimantai volcano was a spherical source located at a depth of 4 km, and that of Iwate volcano was a sill-like oblate spheroid source located at a depth of 10 km.
The GNSS data revealed that the inflation at Hachimantai volcano started in early 2020 with a constant inflation rate. The result also showed the broader inflation signals on Iwate volcano since the beginning of 2024. The inflation on both volcanoes is still growing at the end of 2024. ALOS-2/PALSAR-2 InSAR revealed that the line-of-sight (LOS) shortening, indicating inflation, was located at the center of Hachimantai volcano during 2020-2023, while another LOS shortening signal was also detected on the western part of Iwate volcano since early 2024.
We derived the best-fit geometry for the pressure sources driving the detected inflation to discuss the subsurface volcanic system of the Hachimantai and Iwate volcanoes. The best-fit parameters were optimized using the Markov chain Monte Carlo approach. The best-fit geometry of the pressure source on the Hachimantai volcano was inferred from GNSS and SAR data in 2020–2023, and that of the Iwate volcano was inferred from GNSS and SAR data in 2024. The best-fit geometry of the pressure source at Hachimantai volcano was a spherical source located at a depth of 4 km, and that of Iwate volcano was a sill-like oblate spheroid source located at a depth of 10 km.