Monitoring Land Surface Displacement over Xuzhou (China) in 2015–2018 through PCA-Based Correction Applied to SAR Interferometry

Chen Chen,Tan Tan,Li Li,Liu Liu,Yan Yan,Sun Sun,Zhang Zhang

doi:10.3390/rs11121494

Abstract

Land surface deformation in metropolitan areas, which can cause varying degrees of hazard to both human lives and to properties, has been documented for decades in cities worldwide. Xuzhou, is one of the most important energy and industrial bases in eastern China, and has experienced significant land subsidence due to both excessive extraction of karst underground water and exploitation of mineral resources in recent decades. Furthermore, Xuzhou has recently undergone rapid urbanization in terms of urban expansion and underground construction, which could induce additional pressure on the urban land surface. However, most previous research on land surface deformation in the Xuzhou urban areas has been conducted based on traditional ground-based deformation monitoring techniques with sparse measurements. Little is known about the regional spatiotemporal behavior of land surface displacement in Xuzhou. In this study, a detailed interferometric synthetic aperture radar (InSAR) time series analysis was performed to characterize the spatial pattern and temporal evolution of land surface deformation in central areas of Xuzhou during 2015–2018. A method based on principal component analysis was adopted to correct artifacts in the InSAR signal. Results showed the correction strategy markedly reduced the discrepancy between global navigation satellite systems and InSAR measurements. Noticeable land subsidence (−5 to −41 mm/yr) was revealed widely within the Xuzhou urban areas, particularly along subway lines under construction, newly developed districts, and in old coal goafs. Remarkable consistent land uplift (up to +25 mm/yr) was found to have significantly affected two long narrow areas within the old goafs since 2015. The possible principal influencing factors contributing to the land surface displacements such as subway tunneling, building construction, mining, underground water levels and geological conditions are then discussed.

Highlights

Land surface deformation induced by endogenous forces of the earth and/or anthropogenic activities has been observed worldwide for decades and it has become one of the most prominent geological issues globally [1,2,3,4,5,6]
The persistent scatterer interferometry (PSI) technique was expected to be capable of detecting sufficient coherent points because of the following: (1) The dataset contained a large number of images with dense temporal spacing, and (2) the study area mostly covered an urban area affected by slow continuous surface deformation, meaning the backscattered radar signals would not vary substantially
The traditional long-wavelength artifact correction method provided by Stanford method for persistent scatterers (StaMPS) and the artifact correction method grounded on the theory of principal component (PC) analysis (PCA), recently proposed by Chen et al [6] (Strategy 1), were both found inadequate for high-precision displacement monitoring in this study

Summary

Introduction

Land surface deformation induced by endogenous forces of the earth (e.g., volcanic events, earthquakes, landslides and collapses) and/or anthropogenic activities (e.g., urban construction, mining, oil and groundwater extraction) has been observed worldwide for decades and it has become one of the most prominent geological issues globally [1,2,3,4,5,6]. Land surface deformation threatens human lives and properties, in metropolitan areas with a large population, because it can often result in severe damage both to buildings and to transport infrastructures. China is among those countries that have experienced serious geological disasters because of its complex geological environment, huge population and rapidly growing economy. Accompanying its large scale urbanization, including urban expansion, new underground construction, population migration, as well as the reclamation and exploitation of mining subsidence zones, geological hazards and regional stability problems have become increasingly serious [10]. The monitoring of land surface deformation in Xuzhou on a regular basis is an urgent requirement to prevent any associated risks and to support the integrated sustainable development of the city

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Conclusion