5:15 PM - 7:15 PM
[ACC32-P01] Interferometric SAR Analysis of Ground Deformation in Ulaanbaatar, Mongolia
Keywords:Ulaanbaatar, InSAR, Frost heave, Permafrost
1. Introduction
In the cold regions of Mongolia, repeated freeze-thaw cycles cause frost heave and subsidence, leading to significant ground deformation. Furthermore, with the progression of global warming, permafrost thawing has resulted in ground subsidence in various areas. These ground deformations pose serious concerns for residential areas and infrastructure. In recent years, population growth in Ulaanbaatar has led to the expansion of residential areas into regions prone to frost heave and subsidence. Therefore, understanding the distribution of frost-susceptible soils and permafrost thawing zones, along with measuring ground displacement, is essential for urban planning and environmental monitoring in the Ulaanbaatar region. This study analyzes ground displacement in the Ulaanbaatar area using interferometric SAR (InSAR) analysis.
2. Methodology
In this study, we conducted InSAR analysis using data from ALOS-2 and Sentinel-1, processed with SARScape 5.7. For ALOS-2, we performed SBAS analysis using 13 scenes acquired between 17 July 2017 and 16 September 2024 to assess long-term ground displacement. For Sentinel-1, we applied DInSAR analysis to 18 scenes acquired between 24 March and 7 November 2021, accumulating the results for each period to derive time-series ground displacement during the 2021 thawing season.
3. Results
The ALOS-2 analysis revealed that in the lowland wetland areas of the valley plains on the outskirts of Ulaanbaatar, ground subsidence of 0.10–0.20 m occurred during the thawing period, while similar levels of frost heave were observed during the freezing period. The Sentinel-1 analysis showed that ground subsidence progressed rapidly from April to June, followed by stabilization. Significant ground subsidence was also observed in cut slopes modified by human activity, where subsidence accelerated again from late August onward.
4. Discussion and Conclusion
The primary factors contributing to significant ground deformation in lowland wetland areas are the terrain’s water-retaining characteristics and the presence of fine-grained soils, which promote frost heave and subsidence. In cut slopes, thawing extends to greater depths than before excavation, and the melting of ice lenses near the surface, along with permafrost thawing, likely contributes to increased subsidence. This study also identified significant ground deformation in residential areas and along major roads. Future on-site investigations will further assess the impacts on buildings and infrastructure.
In the cold regions of Mongolia, repeated freeze-thaw cycles cause frost heave and subsidence, leading to significant ground deformation. Furthermore, with the progression of global warming, permafrost thawing has resulted in ground subsidence in various areas. These ground deformations pose serious concerns for residential areas and infrastructure. In recent years, population growth in Ulaanbaatar has led to the expansion of residential areas into regions prone to frost heave and subsidence. Therefore, understanding the distribution of frost-susceptible soils and permafrost thawing zones, along with measuring ground displacement, is essential for urban planning and environmental monitoring in the Ulaanbaatar region. This study analyzes ground displacement in the Ulaanbaatar area using interferometric SAR (InSAR) analysis.
2. Methodology
In this study, we conducted InSAR analysis using data from ALOS-2 and Sentinel-1, processed with SARScape 5.7. For ALOS-2, we performed SBAS analysis using 13 scenes acquired between 17 July 2017 and 16 September 2024 to assess long-term ground displacement. For Sentinel-1, we applied DInSAR analysis to 18 scenes acquired between 24 March and 7 November 2021, accumulating the results for each period to derive time-series ground displacement during the 2021 thawing season.
3. Results
The ALOS-2 analysis revealed that in the lowland wetland areas of the valley plains on the outskirts of Ulaanbaatar, ground subsidence of 0.10–0.20 m occurred during the thawing period, while similar levels of frost heave were observed during the freezing period. The Sentinel-1 analysis showed that ground subsidence progressed rapidly from April to June, followed by stabilization. Significant ground subsidence was also observed in cut slopes modified by human activity, where subsidence accelerated again from late August onward.
4. Discussion and Conclusion
The primary factors contributing to significant ground deformation in lowland wetland areas are the terrain’s water-retaining characteristics and the presence of fine-grained soils, which promote frost heave and subsidence. In cut slopes, thawing extends to greater depths than before excavation, and the melting of ice lenses near the surface, along with permafrost thawing, likely contributes to increased subsidence. This study also identified significant ground deformation in residential areas and along major roads. Future on-site investigations will further assess the impacts on buildings and infrastructure.