Multiscale Decomposition Reveals the Scale-Dependent Drivers of Complex Urban Ground Deformation in Zhengzhou, China

Ground deformation associated with rapid urbanization has emerged as a common global challenge facing cities. However, identifying its contributing mechanisms remains difficult because multiple factors, including groundwater management, engineering loads, and extreme weather events, are often superimposed in space and time. This study proposes a scale-aware analytical framework that integrates Small Baseline Subset InSAR (SBAS-InSAR), Stationary Wavelet Transform (SWT), and Independent Component Analysis (ICA) to separate deformation signals by spatial scale and statistical structure, and then support the interpretation of their potential drivers. The original deformation field is first decomposed into a large-scale background component and a small-scale local component using SWT. ICA is then applied to the large-scale background component to extract two statistically separated deformation modes with distinct spatiotemporal characteristics. These modes are further examined using Least-Squares Cross-Wavelet Analysis (LSCWA) and ancillary hydrological information to evaluate their associations with groundwater-related processes. We applied and validated this framework in Zhengzhou, China, as a representative case. Results show that Zhengzhou exhibits a clear “central uplift and peripheral subsidence” pattern. The large-scale component contains two statistically separated modes. The first mode shows a long-term uplift pattern that is spatially consistent with the groundwater no-take zone and temporally associated with confined-aquifer water-level recovery. The second mode shows an annual oscillation that is coherent with groundwater storage anomaly, with an estimated deformation lag of approximately 1–2 months. The small-scale local component highlights subsidence bowls that are spatially and temporally associated with engineering and land-use features, including newly constructed transportation corridors, high-density building areas, landfills, and waterfront park projects. The proposed framework provides a scale-aware pathway for interpreting complex urban deformation fields and may support more targeted geohazard monitoring and urban planning in areas affected by coupled hydrological and anthropogenic pressures.