Complex Surface Deformation of the Coalfield in the Northwest Suburbs of Xuzhou from 2015 to 2020 Revealed by Time Series InSAR

Abstract

The coalfield in the northwest suburbs of Xuzhou has suffered from extensive land subsidence; however, the temporal nonlinearity and corresponding spatial variation of its surface deformation has not been adequately explored. This study revealed complex surface deformation of the study area from 2015 to 2020 using time series InSAR. A general trend from sharp subsidence to moderated subsidence or even uplift is observed. Three main characteristic types of deformation time series, namely “Subsidence (S)”, “Subsidence–Uplift (S-U)” and “Subsidence–Uplift–Subsidence (S-U-S)”, were detected. Generally, mining activities control the fundamental constraining factors for the surface deformation. Mine closures affect the date of reversal from subsidence to uplift, or in other places the return to subsidence after uplift. Higher deformation rates in preceding sections of the deformation time series are generally correlated with later reversals of deformation trend and higher deformation rates of the succeeding sections of the time series. However, universally applicable spatial and temporal patterns of deformation were not detected, suggesting that surface deformation in the study area is a very complex process. Detailed process and mechanism analysis of surface deformation in the study area should focus on specific mines and pay particular attentions on dewatering and subsequent flooding of mines.