9:15 AM - 9:30 AM
[HDS07-02] Monitoring of active landslides in the Southern Japanese Alps using D-InSAR and optical satellite images: A case study of the Morokozawa landslide
Keywords:D-InSAR, landslide, deformation monitoring, Morokozawa landslide
Introduction
Landslide monitoring is important because landslides cause much damage to society in Japan. In recent years, interferometric SAR techniques have enabled the regional-scale monitoring of the activity of landslides in inaccessible mountainous areas(e.g., Nishiguchi et al. 2017;Usami 2024).
Additionally, 10 years of data accumulation of ALOS-2 allows for the long-term monitoring of active landslides with high accuracy. However, the application of interferometric SAR on landslide monitoring in mountainous regions is still limited. The purpose of this study is to detect and monitor active landslides using differential interferometric SAR (D-InSAR) in the Southern Japanese Alps.The study area is characterized by the dense landslide distribution. This presentation shows temporal changes in the slope movement of the Morokozawa landslide.
Methods
This study used a total of 29 scenes of PALSAR-2 data from October 28, 2014, to August 8, 2023. D-InSAR analysis was applied for these images using RINC ver 0.45 (Ozawa et al., 2016) to calculate the time-series displacement and velocity. We also used optical satellite images of PlanetScope, from 2016 to 2023 to validate the landslide movement. The initiation of the Morokozawa landslide was discovered around August 2023. However, the detailed initiation date and the landslide movement have not been detected yet.
Results and discussion
The results showed that continuous landslide movement from 2016 was detected. The lower part of the landslide slope recorded an average displacement velocity of about 5 cm/yr, although the upper part of the slope had an average displacement velocity of about 0 cm/yr. This result indicates that the lower part of the slope was more active than the upper part of the slope.
The D-InSAR analysis from June 27, 2023, to August 8, 2023, could not detect any significant displacement because of lower coherence values. However, the optical satellite images during the same period showed the expansion of bare lands in the landslide. This result suggests the rapid landslide displacement from June 2023. Further study is necessary to validate the landslide displacement and analyze these active landslides on a regional scale.
Acknowledgments
PALSAR-2 SLC data are shared among PIXEL(PALSAR Interferometry Consortium to Study our Evolving Land Surface), and provided from JAXA under a cooperative research contract with PIXEL. The ownership of PALSAR-2 data belongs to JAXA. This study was supported by ERI JURP 2021-B-03 in Earthquake Research Institute, the university of Tokyo.
References
Nishiguchi, T., Tsuchiya, S. and Imaizumi, F. 2017. Detection and accuracy of landslide movement by InSAR analysis using PALSAR-2 data. Landslides 14: 1483-1490.
Ozawa, T., Fujita, E. and Ueda, H. 2016. Crustal deformation associated with the 2016 Kumamoto Earthquake and its effect on the magma system of Aso volcano. Earth Planets and Space 68: 16.
Usami, S., 2024. Creation and Accuracy Validation of a Hokkaido Active Landslide Data Map Based on TS-InSAR Images Released by the Geospatial Information Authority of Japan. E-journal GEO 19: 132-144 (in Japanese with English abstract).
Landslide monitoring is important because landslides cause much damage to society in Japan. In recent years, interferometric SAR techniques have enabled the regional-scale monitoring of the activity of landslides in inaccessible mountainous areas(e.g., Nishiguchi et al. 2017;Usami 2024).
Additionally, 10 years of data accumulation of ALOS-2 allows for the long-term monitoring of active landslides with high accuracy. However, the application of interferometric SAR on landslide monitoring in mountainous regions is still limited. The purpose of this study is to detect and monitor active landslides using differential interferometric SAR (D-InSAR) in the Southern Japanese Alps.The study area is characterized by the dense landslide distribution. This presentation shows temporal changes in the slope movement of the Morokozawa landslide.
Methods
This study used a total of 29 scenes of PALSAR-2 data from October 28, 2014, to August 8, 2023. D-InSAR analysis was applied for these images using RINC ver 0.45 (Ozawa et al., 2016) to calculate the time-series displacement and velocity. We also used optical satellite images of PlanetScope, from 2016 to 2023 to validate the landslide movement. The initiation of the Morokozawa landslide was discovered around August 2023. However, the detailed initiation date and the landslide movement have not been detected yet.
Results and discussion
The results showed that continuous landslide movement from 2016 was detected. The lower part of the landslide slope recorded an average displacement velocity of about 5 cm/yr, although the upper part of the slope had an average displacement velocity of about 0 cm/yr. This result indicates that the lower part of the slope was more active than the upper part of the slope.
The D-InSAR analysis from June 27, 2023, to August 8, 2023, could not detect any significant displacement because of lower coherence values. However, the optical satellite images during the same period showed the expansion of bare lands in the landslide. This result suggests the rapid landslide displacement from June 2023. Further study is necessary to validate the landslide displacement and analyze these active landslides on a regional scale.
Acknowledgments
PALSAR-2 SLC data are shared among PIXEL(PALSAR Interferometry Consortium to Study our Evolving Land Surface), and provided from JAXA under a cooperative research contract with PIXEL. The ownership of PALSAR-2 data belongs to JAXA. This study was supported by ERI JURP 2021-B-03 in Earthquake Research Institute, the university of Tokyo.
References
Nishiguchi, T., Tsuchiya, S. and Imaizumi, F. 2017. Detection and accuracy of landslide movement by InSAR analysis using PALSAR-2 data. Landslides 14: 1483-1490.
Ozawa, T., Fujita, E. and Ueda, H. 2016. Crustal deformation associated with the 2016 Kumamoto Earthquake and its effect on the magma system of Aso volcano. Earth Planets and Space 68: 16.
Usami, S., 2024. Creation and Accuracy Validation of a Hokkaido Active Landslide Data Map Based on TS-InSAR Images Released by the Geospatial Information Authority of Japan. E-journal GEO 19: 132-144 (in Japanese with English abstract).