11:00 AM - 1:00 PM
[SVC34-P06] Volcano deformation at the lava dome of Unzen Fugen-dake from InSAR observation
Keywords:Unzen Fugen-dake, Heisei-Shinzan, Lava dome, InSAR
Unzen Fugendake, Lava dome
Unzen Fugen-dake , located in Shimabara peninsula, Nagasaki Prefecture, formed a lava dome called Heisei-shinzan due to large-scale eruptive activities between 1990 and 1995.
This lava dome is very unstable because it grew from the eastern edge of the summit to the eastern foot of Mount Fugen. Ground-based observations such as EDM(Electronic Distance Meter ) and GBSAR at the Unzen Restoration Work Office have revealed that the dome has been deforming in the direction of the slope. A part of the lava dome called the Lobe 11 descended about 1.3 m from 1997 to 2021, and there are concerns about large-scale collapse and associated debris avalanche. The purpose of this study is to analyze the behavior of the lava dome from above using InSAR, and to identify the location (horizontal position and depth), direction and driving source of the deformation.
Data
For the interferometric analysis, we used a total of 47 scenes from Path 22 (Descending Left), Path 23 (Descending Right), Path 29 (Descending Left), Path 125 (Ascending Left), and Path 131 (Ascending Right) observed by ALOS-2/PALASAR-2 from 2014 to 2021.
Results
The crustal deformation of a lava dome was captured by InSAR. The spatial distribution of the deformation was estimated from the interferogram, and it was found that the spatial scale of the deformation was about 1.5 km, which could be divided into a large unit that deformed the whole dome in the slope direction and independent units in the eastern and western parts of the dome . The western part is located at the clastic lava mound at the top of Heisei-shinzan, and the eastern part is located near Lobe 11 (hereinafter referred to as clastic lava mound and Lobe 11). In the eastward observation (Ascending Right and Descending Left), the clast lava mound and lobe 11 showed the extension of the line of sight distance of about 12cm/year. In the westward observation (Ascending Left and Descending Right), the line-of-sight distance of clastic lava mound is about 5 cm/year, and that of lobe 11 is ambiguous due to the effect of layover, and the amount and pattern of variation vary from interferogram to interferogram. The dome has been deforming at a constant rate over the period of 2014-2021, with out significant temporal changes in the rate or pattern of change. In the future, we will compare the shape of the dome with that of the former mountain topography and quantitatively evaluate the amount of variation.
Acknowledgments
We thank Dr. Shohei Narita of Kyoto University for his advice on the InSAR analysis. The ALOS-2/PALSAR-2 data used in this study was provided by JAXA and shared by the PIXEL group. This study was supported by ERI JURP 2021-B-03 in Earthquake Research Institute, the University of Tokyo. RINC (Ozawa et al., 2016) was used as an analysis tool. In addition, in the process of processing, the numerical map 10m mesh (elevation) of GSI was used.
Unzen Fugen-dake , located in Shimabara peninsula, Nagasaki Prefecture, formed a lava dome called Heisei-shinzan due to large-scale eruptive activities between 1990 and 1995.
This lava dome is very unstable because it grew from the eastern edge of the summit to the eastern foot of Mount Fugen. Ground-based observations such as EDM(Electronic Distance Meter ) and GBSAR at the Unzen Restoration Work Office have revealed that the dome has been deforming in the direction of the slope. A part of the lava dome called the Lobe 11 descended about 1.3 m from 1997 to 2021, and there are concerns about large-scale collapse and associated debris avalanche. The purpose of this study is to analyze the behavior of the lava dome from above using InSAR, and to identify the location (horizontal position and depth), direction and driving source of the deformation.
Data
For the interferometric analysis, we used a total of 47 scenes from Path 22 (Descending Left), Path 23 (Descending Right), Path 29 (Descending Left), Path 125 (Ascending Left), and Path 131 (Ascending Right) observed by ALOS-2/PALASAR-2 from 2014 to 2021.
Results
The crustal deformation of a lava dome was captured by InSAR. The spatial distribution of the deformation was estimated from the interferogram, and it was found that the spatial scale of the deformation was about 1.5 km, which could be divided into a large unit that deformed the whole dome in the slope direction and independent units in the eastern and western parts of the dome . The western part is located at the clastic lava mound at the top of Heisei-shinzan, and the eastern part is located near Lobe 11 (hereinafter referred to as clastic lava mound and Lobe 11). In the eastward observation (Ascending Right and Descending Left), the clast lava mound and lobe 11 showed the extension of the line of sight distance of about 12cm/year. In the westward observation (Ascending Left and Descending Right), the line-of-sight distance of clastic lava mound is about 5 cm/year, and that of lobe 11 is ambiguous due to the effect of layover, and the amount and pattern of variation vary from interferogram to interferogram. The dome has been deforming at a constant rate over the period of 2014-2021, with out significant temporal changes in the rate or pattern of change. In the future, we will compare the shape of the dome with that of the former mountain topography and quantitatively evaluate the amount of variation.
Acknowledgments
We thank Dr. Shohei Narita of Kyoto University for his advice on the InSAR analysis. The ALOS-2/PALSAR-2 data used in this study was provided by JAXA and shared by the PIXEL group. This study was supported by ERI JURP 2021-B-03 in Earthquake Research Institute, the University of Tokyo. RINC (Ozawa et al., 2016) was used as an analysis tool. In addition, in the process of processing, the numerical map 10m mesh (elevation) of GSI was used.