Land Subsidence Monitoring And Correlation Analysis With Ground Fluid Exploitation Using Time Series InSAR Technique Over The Yellow River Delta(China)

The Yellow River(Huanghe) delta, the youngest and most rapid growth typical coastal region in C hina, having a unique formational background and sedimentary setting, undergoes severe land subsidence due to the combination effects of tectonic movement, sediment consolidation and compaction, especially the frequent anthropogenic activities. The land subsidence results in Yellow River delta increasingly vulnerable to secondary disasters, such as storm surge, coastal flooding, saltwater intrusion and infrastructure destabilization; meanwhile normal social economy of the local citizens and ecology environment are highly threatened by the ongoing rapid land subsidence. Therefore, it will be of great significance in characterizing the full and detail spatial and temporal distribution and evolution of the land subsidence, processing its causing, providing technological and decision support for disaster prevention and mitigation, scientifically guiding the natural resources development and utilization, protecting the ecological environment of Yellow River delta sustainable development.As a new type of Earth observation technique, InSAR has the advantages of large coverage, high spatial and temporal resolution and high accuracy and has been widely used in many geosciences fields, especially in surface deformation disaster monitoring field. However, affected by many factors, i.e. atmospheric phase screen, topographic errors, spatial and temporal decorrelation and thermal noises and so on, the monitoring accuracy and application field of traditional InSAR are greatly limited. In order to overcome the limitations and improve detection ability and accuracy, time series InSAR technique, represented by persistent scatterer(PS) InSAR and small baseline subset(SBAS) InSAR, were developed to eliminate the errors of traditional InSAR and provide long time high accuracy, high spatial and temporal resolution surface deformation results.Taking the large area and complicated land subsidence of Yellow River as the research object, we studied the method to obtain high precision surface deformation utilizing time series InSAR technique over the special environment area in coastal region. The spatial and temporal distribution and evolution characterization of whole surface deformation and regional land subsidence are analyzed. Further research are focusing on the interpretation of the deformation mechanism and modeling analysis according to the field data. All these studies extended the depth and breadth of the application of time series InSAR over Yellow River delta. This paper mainly includes:(1) Traditional InSAR and time series InSAR technique are systematically reviewed and analyzed. There are several special issues in the process of monitoring surface deformation over coastal region of Yellow River delta: traditional InSAR can not obtain reliable surface deformation result; traditional time series InSAR can not identify and select high coherent points in sufficient density over low coherent area affected by temporal decorrelation; phase of the point is unstable and has large errors due to change in look angle and so on. Based on the time series InSAR proposed by Hopper, this article gives a detail analysis on the high coherent point identification and selection over low coherent area, band pass filter in spatial and temporal domain, phase unwrapping method, phase error elimination and the whole data processing scheme.(2) This paper studies the long time series, high spatial and temporal resolution and high precision surface deformation over Yellow River delta using time series InSAR technique. Large area land subsidence spatial and temporal distribution, evolution characterization and land subsidence pattern are obtained, the spatial and temporal correlation between large area land subsidence and ground water exploitation, the correlation between seasonal precipitation with nonlinear surface deformation are analyzed. The results indicated that the large area land subsidence over Yellow River delta is primarily caused by intense groundwater withdrawal, which induce the aquifer and overburden subsidence.(3) Focusing on the regional land subsidence in oil field, this paper gives a detail analysis on its spatial and temporal distribution, evolution characterization and correlation with faults distribution. The regional subsidence is modeled using three different models: the spherical source Mogi type model, the finite prolate spheroid model and the dual finite prolate spheroid model. Furthermore, the optimal model parameters, adaptability, reliability and accuracy of the three models are compared and analyzed. This article has resolved that the regional land subsidence cone over oil field, which is likely caused by hydrocarbon exploitation and reservoirs compaction.