InSAR Time Series Analysis to Evaluate Subsidence Risk of Monumental Chandigarh City (India) and Surroundings

Abstract

Groundwater depletion is one of the serious geoenvironmental issues causing ground subsidence, which damage buildings, infrastructures and causes loss of life. The quantitative and qualitative evaluation of groundwater variability requires multiple approaches to measure hydraulic head level and geodetic deformation. In this study, we have made efforts to integrate multiple hierarchical space-borne data, including Gravity Recovery and Climate Experiment (GRACE), Sentinel-1 Interferometric Synthetic Aperture Radar (InSAR), geological and hydrological data, to quantify subsidence in Chandigarh city and its surroundings. First, we conducted New-Small BAseline Subsets (NSBAS) and pointwise persistent scatterer (PS) InSAR techniques in parallel, using three-years Sentinel-1 data showing a vertical subsidence up to 120 mm/year around fluvial sediment deposits. Further, correlation analysis of hydraulic/climatic measurements clearly shows the subsidence associated with the groundwater depletion. The pattern of PS points shows the instability of structures associated with the ground subsidence over the central city areas. The monumental architectures designed by Le Corbusier in the northern sectors are outside of the main subsidence area. In the target area, the magnitude of subsidence and surface deformation due to groundwater depletion depending on the subsurface geophysical environment and the anthropogenic activities within the region and surroundings. The results provided a case of monitoring scheme using multiresolution satellite data about the subsidence and associated consequences due to groundwater depletion.

Comments on Kumar et al. (2023), Evidence of Strain Accumulation and Coupling Variation in the Himachal Region of NW Himalaya From Short Term Geodetic Measurements. Tectonics https://doi.org/10.1029/2022TC007690.

“…Further, by the authors' own admission (Kumar et al, 2023), the four sites (CHPU, SOLN, SANR, SHLS) closest to the KTF-1 segment are malfunctioning and therefore the authors decided not to use the unreliable data from these sites in subsequent analysis. In fact, one of the GNSS sites CHPU is located within a strongly deforming piedmont zone (Kim et al, 2023;Sahadevan and Pandey, 2023). Therefore, in view of the quality of the datasets and site conditions, it is felt that Kumar et al (2023) could provide no clarity on the sense of movement, and ambiguity about the nature of slip/offset on the KTF-1 remains, both in the long-term and short-term.…”