Integrated dislocation and strain models for 3-D coseismic deformation field from GNSS and InSAR

SUMMARY Accurate 3-D coseismic deformation fields are critical for fault mechanics analysis and hazard assessment, but the sparse distribution of Global Navigation Satellite System (GNSS) stations often limits reconstruction accuracy. This study proposes Integrated Dislocation and Strain Models (IDSM) that seamlessly integrate GNSS and Interferometric Synthetic Aperture Radar (InSAR) data. This is achieved by combining a surface-constrained strain model and a subsurface-constrained dislocation model, which adaptively optimizes multisource data weights through Variance Component Estimation (VCE), challenging the traditional reliance on uniformly distributed observations. Simulation experiments demonstrate that under insufficient GNSS coverage, this method improves deformation recovery accuracy by 10 per cent to 70 per cent in the vertical, north and east components compared to the ESISTEM-VCE (Extended Simultaneous and Integrated Strain Tensor Estimation from Geodetic and Satellite Deformation Measurements-VCE) method, with particularly significant enhancement in the north component. Applied to the 2021 Yangbi MW6.4 and Maduo MW7.4 earthquakes, the study reveals distinct deformation patterns: the Yangbi event exhibits right-lateral strike-slip rupture with a maximum east–west extensional displacement of 87 mm and vertical subsidence of 59.8 mm, showing antisymmetric horizontal deformation around the epicentre. In contrast, the Maduo earthquake is dominated by left-lateral strike-slip motion, with east–west displacement reaching 1.4 m, while north–south and vertical deformations display patchy distributions along the fault. Error analysis confirms accuracy improvements over the ESISTEM–VCE method. For the Yangbi earthquake, the Root Mean Square Error (RMSE) decreased by 50 per cent (east), 64 per cent (north) and 44 per cent (vertical) at GNSS validation points. Corresponding improvements of 6.1 per cent (east) and 53.5 per cent (north) were achieved for the Maduo earthquake.