Surface deformation assessments in Hanoi, Vietnam using ALOS PALSAR interferometry

Surface deformation is a well known phenomenon for many years in the urban area of Hanoi city, the capital of Vietnam. Although much of the effort made by researchers has focused on detecting and monitoring the deforming rate in this city, there is no data available for the newly administrative districts due to a large-scale extent needed to be covered and the limitation of conventional monitoring methods. In the last decade, Interferometric Synthetic Aperture Radar (InSAR) has proven as a powerful geodetic technique for detecting and monitoring small scale displacements of the Earth surface with millimetric precision. Therefore, we use the cutting-edge radar technique Persistent Scatterer InSAR to assess the ground deformation of nearly full area of the new Hanoi. A timeseries ALOS PALSAR stack that covered the period between 2007 and 2009, captured in different data modes is jointly analyzed to derive the deforming information. The results suggest us that the subsidence rate in the surrounding urban districts of Hanoi (namely Tu Liem, Ha Dong, Thanh Xuan and Hoang Mai) reach up to -45mm per year, is at severe level. We found two deformation regions that have never been observed before which are northeastern Luong Son subsiding area and southern My Duc uplifting area. The reasons of these phenomena were considered as massive groundwater extraction and infrastructure constructions. We also analyze the temporal evolution of some reference PS points as well as compare with previous studies in order to evaluate the consistent of the results. Further work should be focused on the surface deformation of northern sub-urban districts and integrating next-gen SAR sensors for better understanding the deforming patterns of this area.