9:30 AM - 9:45 AM
[STT36-03] Landslide and its displacement along the Marsyangdi River, Nepal detected by differential interferometric SAR
Keywords:D-InSAR, ALOS-2, Landslide
Nepal has the areas prone to be affected by landslides in the world due to the steep topography and complex geological structure caused by plate collision. However, due to the highly undulating topography, on-site monitoring of landslide displacement is difficult, and the number of observation cases is limited. In this study, we attempted to monitor landslide displacement using D-InSAR and to elucidate the characteristics of landslide displacement along the Marsyangdi River, which was considered to be a high risk area of landslides in the previous studies.
A total of 17 ALOS-2 data observed from November 20, 2014 to August 6, 2020 was used in this study, and RINC0.41 software developed by Ozawa et al. (2016) was used for D-InSAR analysis. The D-InSAR images were projected onto a map using ArcGISpro for topographic interpretation and displacement analysis (Fig. 1).
Two landslides were interpreted on the right bank of the Marsyangdi River (28°21'56 "N, 84°23'25 "E; 28°21'4 "N, 84°23'17 "E). These sites (Fig. 2) are located about 1.5 km north of the Main Central Thrust (MCT), where a large landslide feature are identified and gneiss is distributed. The resulting displacement analysis using multi-temporal D-InSAR images showed that the displacement continued from September 15, 2015 to December 26, 2019 at the shortest. The maximum displacement was calculated from the D-InSAR image of October 18, 2018 - March 21, 2019 and it was compared with the precipitation. The results showed that the rate of displacement did not increase during the rainy season, but rather accelerated immediately after the rainy season (Fig. 3). In addition, we confirmed that top of the landslide body is located on the knick line on the slope, and that the lower part of the landslide body was displaced just after the displacement of the upper part (Fig. 1).
It is inferred that the geology fractured by the MCT is involved in this movement. The relationship with precipitation suggests that there is a temporal gap between landslide displacement and high precipitation. Since the top of the landslide body is located on the knick line, the topography associated with the down cutting after the last glacial period may contribute to the landslide behavior, and this point will be discussed in detail in the future.
Acknowledgement
This study was supported by KAKEN 19H01368, 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. AW3D data (https://www.aw3d.jp/) were used for producing shaded relief map.
References:
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 Spase, 68: 16.
Yagi H, Sato G, Sato HP, Higaki D, Dangol V, Amatya SC, Slope deformation caused Jure landslide 2014 along Sun Koshi in lesser Himalaya and effect of Gorkha earthquake 2015, In Vilímek V, Wang F, Strom A, Sassa K, Bobrowsky PT, Takara K (eds.), Understanding and Reducing Landslide Disaster Risk, 5, 65-72, Springer, 2020.
A total of 17 ALOS-2 data observed from November 20, 2014 to August 6, 2020 was used in this study, and RINC0.41 software developed by Ozawa et al. (2016) was used for D-InSAR analysis. The D-InSAR images were projected onto a map using ArcGISpro for topographic interpretation and displacement analysis (Fig. 1).
Two landslides were interpreted on the right bank of the Marsyangdi River (28°21'56 "N, 84°23'25 "E; 28°21'4 "N, 84°23'17 "E). These sites (Fig. 2) are located about 1.5 km north of the Main Central Thrust (MCT), where a large landslide feature are identified and gneiss is distributed. The resulting displacement analysis using multi-temporal D-InSAR images showed that the displacement continued from September 15, 2015 to December 26, 2019 at the shortest. The maximum displacement was calculated from the D-InSAR image of October 18, 2018 - March 21, 2019 and it was compared with the precipitation. The results showed that the rate of displacement did not increase during the rainy season, but rather accelerated immediately after the rainy season (Fig. 3). In addition, we confirmed that top of the landslide body is located on the knick line on the slope, and that the lower part of the landslide body was displaced just after the displacement of the upper part (Fig. 1).
It is inferred that the geology fractured by the MCT is involved in this movement. The relationship with precipitation suggests that there is a temporal gap between landslide displacement and high precipitation. Since the top of the landslide body is located on the knick line, the topography associated with the down cutting after the last glacial period may contribute to the landslide behavior, and this point will be discussed in detail in the future.
Acknowledgement
This study was supported by KAKEN 19H01368, 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. AW3D data (https://www.aw3d.jp/) were used for producing shaded relief map.
References:
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 Spase, 68: 16.
Yagi H, Sato G, Sato HP, Higaki D, Dangol V, Amatya SC, Slope deformation caused Jure landslide 2014 along Sun Koshi in lesser Himalaya and effect of Gorkha earthquake 2015, In Vilímek V, Wang F, Strom A, Sassa K, Bobrowsky PT, Takara K (eds.), Understanding and Reducing Landslide Disaster Risk, 5, 65-72, Springer, 2020.