A joint InSAR-GNSS workflow for correction and selection of interferograms to estimate high-resolution interseismic deformations

Knowledge of the spatial distribution of interseismic deformations is essential to better understand earthquake cycles. The existing methods for improving the reliability of the obtained deformations often rely on visual inspection and prior model corrections that are time-consuming, labor-intensive, and do not consider the spatial distribution of interseismic deformations. Interferometric Synthetic Aperture Radar (InSAR) data provides wide-scale coverage for interseismic deformation monitoring over a wide area. However, the interseismic signal featured as millimeter-scale and long-wave deformations is often contaminated with noise. In the present study, a new workflow to correct the interferometric phase and quantitatively select interferograms is proposed to improve the accuracy of interseismic deformation measurements. Initially, the Generic Atmospheric Correction Online Service (GACOS), Intermittent Code for Atmospheric Noise Depression through Iterative Stacking (I-CANDIS), and plate model are combined to correct the atmospheric screen and long-wave ramp phase. Subsequently, the Pearson’s Correlation Coefficient (PCC) between the interferometric phase and the Global Navigation Satellite System (GNSS) constrained interseismic model as well as the STandard Deviation (STD) of the interferometric phase are introduced as criteria to optimize the selection of interferograms. Finally, the intermittent stacking method is used to generate an average velocity map. A comprehensive test using Sentinel-1 images covering the Haiyuan Fault Zone validate the effectiveness of our workflow in measuring interseismic deformations. This demonstrates that the proposed joint InSAR-GNSS workflow can be extended to study the subtle interseismic deformations of major fault systems in Tibet and worldwide.