Understanding the Spatial-Temporal Characteristics of Land Subsidence in Shenzhen under Rapid Urbanization Based on MT-InSAR.

Land subsidence is a common geological hazard in urban areas. It can be caused by human activities such as land reclamation and subway construction. However, rapid urbanization can accelerate the progress of these activities. Therefore, spatial-temporal analysis of land subsidence can provide a guarantee for rapid urbanization progress. In this study, Shenzhen, one of the fastest urbanizing cities in China, is selected for continued land subsidence monitoring. We collected 153 Sentinel-1A images from December 2015 to July 2021 and utilized an interferometric point target analysis method to generate the land subsidence in Shenzhen. Additionally, we analyzed the relationship between land subsidence and typical urbanization progress: land reclamation, transportation network, and urban construction. The results show that land subsidence mostly occurs in the western reclamation area, with a maximum rate of -74.9 mm/a in Qianhai Bay. Areas with larger quaternary marine sediment thickness in the range of 10-20 m are more likely to experience subsidence. Obvious subsidence (<-20 mm/a) along the subway mainly occurred on Lines 11 and Line 5, which is inversely proportional to the distance from the metro. The correlation coefficient is -0.197. Areas with low road densities have a high probability of experiencing great subsidence. A relationship between land subsidence and building construction in the Guangming district is found. Obvious subsidence (<-20 mm/a) mainly occurred in the building areas, with a percentage of 43.48%.