InSAR Detection of Ground Deformation in Megalopolises of Pearl River Delta.

摘要

Megalopolises in the Pearl River Delta, including Guangzhou and Hong Kong, have experienced various degree of ground subsidence. The causes can be divided into two categories: natural subsidence and the human-induced subsidence. Monitoring the ground subsidence can not only help people to find out the distributions in both spatial and temporal fields, but also guide people to minimize the hazard ahead. Thus, it is significant to monitor the ground subsidence accurately, timely and frequently. This dissertation research uses the Environmental Satellite Advanced Synthetic Aperture Radar (ENVISAT ASAR) data received at the Chinese University of Hong Kong Satellite Remote Sensing Receiving Station and SAR Interferometry (InSAR) technology as a powerful tool for large-scale ground deformation monitoring in Guangzhou and Hong Kong areas.;Persistent Scatterer Interferometry (PSI) method is used to detect ground deformation in the urban area of Guangzhou city. A ground deformation rate map with scattered distribution of point targets shows the maximum subsidence (rise) rate as high as -26 to -20 mma-1 (16-21 mma-1 ), implying that the study area is an active zone for ground deformation. Based on the point target map, a contour ground deformation rate map is generated. All the six ground collapse accidents that occurred in 2007-2008 fall within the subsidence zones, qualitatively validating the IPTA results. Ground subsidence and geological conditions on Datansha Island are examined. The results indicate that the local geological conditions and underground engineering projects are responsible for ground subsidence and ground collapse accidents occurred there. To interpret the distribution of active ground subsidence zones, a local geological map is used as a reference for generating a series of thematic maps. The results show that geological faults, rock distribution, over-development, and underground engineering projects may be four factors leading to the distribution of the active ground subsidence zones.;The Hong Kong International Airport (HKIA) was built on a site of 12.5 km2, of which 75% is reclaimed foundation. Thus, the stability of ground foundation of HKIA is of public concern. I use the PSI method and ENVISAT ASAR data to detect the residual settlement rate from 19 April 2006 to 9 January 2008. I use ground truth data to develop empirical correction models for correcting systematic biases in the ASAR PSI-detected settlement rate. The corrected data follow the Lorentz distribution well, implying that the residual settlement process is dominated by two modes or categories of settlement rates. I find unreasonable positive values of the ASAR PSI-detected annual ground settlement rate, which follow a normal distribution. I draw a scatter plot with ground deformation rate value and coherence value of each point targets. Point targets with lower coherence values and greater positive values are extracted and drawn on a geographical map. Most of these point targets are located at the airport Midfield, which is under construction. A ground settlement rate map of HKIA shows that an area of the Passenger Terminal Building, and an area of the Southern Runway are two relatively stable areas, and one major continuous settlement area covers the airport Midfield. General spatial distribution patterns of ASAR PSI-detected ground settlement rate agree well with model-predicted residual settlement rates.