Crustal Deformation Monitoring Based On D-InSAR Technology In Hangzhou Area And Study On Deformation Mechanism

Differential interferometric synthetic aperture radar (D-InSAR) imaging technology was emerging at the end of the 20th century. It uses the information of the phase of two SAR images to extract height information and brings a revolution for geodesy. It has the advantages of synthetic aperture radar (SAR), such as penetrating the cloudy layer or the barrier, carrying on all-weather work all day and all night, wide mapping area, real-time imaging and high flexibility etc. These can't be get through optical method.Present crustal deformation information is intuitive characteristics of tectonic movement of the crust, and also reflects the regional characteristics of the crustal movement. The current characteristics of crustal deformation of Hangzhou area was monitored by the D-InSAR technology and the crustal deformation mechanism was discussed deeply combined with regional geological data, geophysical data, hydrogeology and drilling data etc. The paper falls into the following parts:1. The basic theories and methods of D-InSAR technology are studied and propose the "three-pass" method as the best monitoring model of Hangzhou area.2. Make a deep research on the formation mechanism and mathematical models of the speckles of SAR images, propose a new method of noise removal of SAR image based on improved wavelet soft-thresholding method, and in accordance with smoothness index and edge preservation index prove that the comprehensive performance of this method is better than other traditional filters such as median filter, Frost filter, Lee filter, wavelet hard-thresholding and soft-thresholding.3. Analysize the theory and methodology of phase unwrapping, demonstrate and compare the current seven popular phase unwrapping algorithms, analysize their advantages and disadvantages, select statistical-cost network-flow algorithm as the most suitable algorithm used in Hangzhou area and evaluate its effectiveness and efficiency.4. Propose a new image fusion method based on lifting wavelet transformation and carry on visual interpretation and quantitative evaluation with IHS transform, PCA transform, Brovey transform and so on. Extract the information of the faults in Hangzhou area by means of edge enhancement, directional enhancement, high-pass filter, texture analysis etc. and collect gravity and areomagnetic anomalies data, shallow artificial seismic exploration data, borehole data and dating data etc. to validate the interpreted results. The results show that the faults of Hangzhou area have been active since the Quaternary, but the possibility seems less since the late Pleistocene.5. Get the crustal deformation map of Hangzhou area between 1997 and 2000. the deformation shows the characteristic of area and divides into three relative obvious regions. At the same time, the subsidence areas show sector distribution and diffusion obviously. There is no linear structure in the inner and edge of the deformed zone, which shows that the deformation has less association with the faults.5. Make a careful research on the crustal deformation mechanism of Hangzhou area combined with regional structural background, Quaternary sedimentary succession and characteristics of ground water. Conclude that it is not the major faults of Hangzhou area but long time groundwater exploitation that control the crustal deformation of Hangzhou area. At the same time, draw isopach, contour and three-dimensional strata map of Hangzhou area and prove that the thickness of Holocence is the main factors. In addition, the unit subsidence of clay layer is far larger than sand and gravel layer in low pressure condition and the subsidence was mainly concentrated in the aquifer, less consolidation or compressible consolidation of the thick clay layer.The preliminary results show that using D-InSAR technology for monitoring the ground deformation of Hangzhou area is relatively satisfied. However, monitoring the ground deformation of eastern cities of China needs further research and improvement and there are many urgent problems to solve in specific applications, for example, despeckling, time decorrelation, baseline decorrelation and the improvement of phase unwrapping algorithms and so on.