Study region: The Taiyuan Basin in northern China, a semi-arid region where prolonged groundwater overexploitation has resulted in severe land subsidence and irreversible aquifer storage loss. Study focus: By integrating Sentinel-1 InSAR time series analysis (2015-2020) and groundwater level measurements, we developed a geophysical model to quantify seasonal deformation signals and the time-lagged relationships between land subsidence and groundwater level changes. Through incorporating time-lag corrections, we refined estimations of the elastic skeletal storage coefficient Ske and groundwater storage variations. A novel method was proposed to separate elastic deformations in sand and clay layers based on their distinct hydraulic response characteristics. New hydrological insights for the region: Land subsidence lags groundwater level changes by an average of 39 days, revealing delayed compaction dominated by low-permeability clay layers. Recoverable groundwater storage accounts for merely 5 % of total losses, indicating that most of subsidence results from inelastic clay compression, which underscores a critical risk of permanent aquifer storage capacity depletion. The observed 54-day delayed response in clay layers correlates with their thickness and multi-layered structure, offering critical parameters for predicting the structure of multi-layered aquifer systems. This study systematically elucidates the groundwatersubsidence coupling mechanisms, providing new insights for characterizing over-exploited aquifers and advancing sustainable groundwater resource management worldwide.