10:45 AM - 12:15 PM
[STT39-P04] Study on detection of deep-seated landslides induced surface deformation using SAR interferometry
-Case study in Tatsuno Town, Nagano Prefecture, in the Mino terrene distribution area-
Keywords:deep-seated landslides, gravity-deformed slopes, ALOS-2, differential interferometric analysis
It has become clear that deep-seated landslides occur when slopes are deformed by gravity in the characteristics geological structure (Chigira et al., 2013), and it is possible to predict the place of occurrence using these as keys. Surface deformation of gravity-deformed slopes can be captured by interferometric SAR analysis, and there are many reports on landslide topography with displacement of several centimeters per year (Sato et al., 2012, Ishitsuka et al., 2017, etc.).However, the displacement of gravity-deformed slopes with the potential for deep-seated landslides is thought to be a few millimeters per year at most, and there are few extraction cases in Japan, where much of the mountainous terrain is covered by plantations.
In this study, we examined the time-series displacement of slopes from differential interference analysis at multiple times for six deep-seated landslide danger slopes identified by Matsuzawa and Kimura (2022). The survey site is located downstream of the Yokogawa River in Tatsuno Town, Nagano Prefecture, where the Mino terrene, an accretionary complex of the Jurassic period, is distributed. The data used for the differential interferometric analysis are the ALOS-2 data of the Ascending. Six scenes captured at intervals of about one year from March 18, 2016 to February 26, 2021 were analyzed in pairs about every year. In December 2022, continuous observations using tiltmeter began on two of the slopes at the deep-seated landslides danger slopes, and slope displacements have been confirmed.
The analysis identified slope variations with a cumulative trend on four deep-seated landslide danger slopes. The accumulated displacement for 6 years was about 2 mm at maximum, but the displacement was in the direction of subsidence in the upper part of the deep-seated landslide danger slope, and in the direction of extrusion in the lower part, suggesting the possibility of grasping the gravitational deformation. In addition, the direction of deformation of the deep-seated landslide danger slope was consistent with the observation results from the tiltmeter.
This time, we used the ALOS-2 data acquired in the winter season of February and March, but we plan to analyze the autumn data and confirm whether the same tendency appears. Since the slope variation has been observed by tiltmeter since December 2022, we plan to compare the displacement by tiltmeter with the differential interferometric analysis using ALOS-2 data acquired after this time.
Acknowledgement
This study was supported by KAKEN 22K14106, and data used in this study were provided by PIXEL (PALSAR Interferometry Consortium to Study our Evolving Land surface) under a cooperative research (2021-B-03) contract with ERI, Univ. of Tokyo. Differential interferometric analysis was performed using RINC and RINC GUI provided by PIXEL.
In this study, we examined the time-series displacement of slopes from differential interference analysis at multiple times for six deep-seated landslide danger slopes identified by Matsuzawa and Kimura (2022). The survey site is located downstream of the Yokogawa River in Tatsuno Town, Nagano Prefecture, where the Mino terrene, an accretionary complex of the Jurassic period, is distributed. The data used for the differential interferometric analysis are the ALOS-2 data of the Ascending. Six scenes captured at intervals of about one year from March 18, 2016 to February 26, 2021 were analyzed in pairs about every year. In December 2022, continuous observations using tiltmeter began on two of the slopes at the deep-seated landslides danger slopes, and slope displacements have been confirmed.
The analysis identified slope variations with a cumulative trend on four deep-seated landslide danger slopes. The accumulated displacement for 6 years was about 2 mm at maximum, but the displacement was in the direction of subsidence in the upper part of the deep-seated landslide danger slope, and in the direction of extrusion in the lower part, suggesting the possibility of grasping the gravitational deformation. In addition, the direction of deformation of the deep-seated landslide danger slope was consistent with the observation results from the tiltmeter.
This time, we used the ALOS-2 data acquired in the winter season of February and March, but we plan to analyze the autumn data and confirm whether the same tendency appears. Since the slope variation has been observed by tiltmeter since December 2022, we plan to compare the displacement by tiltmeter with the differential interferometric analysis using ALOS-2 data acquired after this time.
Acknowledgement
This study was supported by KAKEN 22K14106, and data used in this study were provided by PIXEL (PALSAR Interferometry Consortium to Study our Evolving Land surface) under a cooperative research (2021-B-03) contract with ERI, Univ. of Tokyo. Differential interferometric analysis was performed using RINC and RINC GUI provided by PIXEL.