Spatial-temporal evolution characteristics of land subsidence in Dongguan City based on improved InSAR technology

Dongguan City is an important city of Pearl River Delta urban agglomeration and Guangdong-Hong Kong-Macao Greater Bay Area. Deep unconsolidated soft soil and its land subsidence have become a representative regional geological disaster in the Bay area, affecting the safety of urban geological environment. In order to study the development features and spatial-temporal evolution characteristics of land subsidence in Dongguan City, 137 sentinel-1 SLC SAR images covering whole Dongguan City were processed by improved InSAR technology, and the dynamic evolution characteristics of land deformation from June 2015 to June 2020 was analyzed. The results show that: (1) The land surface subsidence and deformation are stable in the whole region, and the subsidence developing areas account for 34.6% of the total urban area. The serious subsidence areas are mainly concentrated in Mayong Town, Daojiao Town, Hongmei Town, Zhongtang Town, Shatian Town and Binhai Bay New Area. (2) Most of the subsidence points are in the slow developing stage, the annual average subsidence rate is within 20 mm/yr, and the accumulated settlement is less than 1000 mm. (3) Combined with deformation monitor results and field investigation, land subsidence hazard has a great correlation with the coupling effect of deep soft soil development and human engineering activities. This method can better identify and reflect the temporal and spatial evolution characteristics of soft land subsidence development in urban area, and provide technical support for disaster early warning, mitigation and management.