Monitoring and analysis of subsidence along Ri-Lan high-speed railway at Juye coalfield based on the improved MT-InSAR

Farmland is distributed along the Ri-Lan high-speed railway, which may lead to a failure of interferometric synthetic aperture radar(InSAR) due to the temporal decorrelation.Besides, there is a lack of persistent scatterer(PS) for multi-temporal InSAR(MT-InSAR) analysis in the rural area with sparse buildings.It is a potential solution to these problems by using only the SAR data acquired from October to early April of next year to improve the coherence of interferogram and by incorporating the PS and distributed scatterer(DS) to increase the number of coherent point.Nevertheless, due to the limitation of imaging capability of spaceborne SAR system, the number of SAR images available over a period of about six months is often too small to accurately estimate the covariance and coherence matrix of DS(especially in the case of low coherent scenarios),which will degrade the performance of traditional methods.Fisher information index is a common measure for the information content that a random variable carries about an unknown parameter, thereby a new methodology based on the Fisher information index is presented to robustly estimate the DS phase.The new methodology is compared with the related traditional methods via simulation analysis and real data experiments with Sentinel-1 data.The results show that the presented methodology performs better.Besides, a SBAS baseline approach incorporating both PS and DS is presented to increase the number of observation equations, improve the coherence of interferograms and robustly estimate the ground deformation.The ground subsidence along Ri-Lan high-speed railway between October 2020 and April 2021 is extracted employing the presented approach by using C-band SAR acquisition constructed from two tracks of Sentinel-1 data over the region.Then, the characteristics and evolution of the ground subsidence is investigated by comparing with the previous data.The results show that the ground subsidence can be extracted based on a small SAR dataset acquired from October to early April in northern China by using the approach presented.The study also shows that the ground displacement rate ranges from-3.5 to-0.5 cm/a and agrees with the previous measurements without significant worsening.Besides, a secondary subsidence, probably caused by the groundwater outflow and fault instability due to mining, appears further away from the main subsidence basin and affects the regular operation of Ri-Lan high-speed railway, which needs to be further investigated.