Determining The Displacement Field Of Chi-Chi Taiwan Earthquake Using Doris And Chelungpu Fault Slip Inversion

During the last 15 years, InSAR as a relatively new remote sensing technique has been widely used to study the displacement related to earthquake, volcanoes, landslides, oilfields and mines. The main advantages of InSAR for studying seismic deformation are the low cost and high spatial resolution. In addition, the available SAR data covers most subaerial areas in the world. This is particularly important because many earthquakes occur in areas where no conventional geodetic measurements exist. The work is dedicated to the understanding of the principles of InSAR and its application to the study of displacements caused by earthquake.Based on the traditional InSAR elevation model, I develop an improved one which expresses the direct relationship between height and phase. In this model and other available InSAR models, the parallel ray approximation or far-field approximation is widely used. I analyze the errors introduced by the parallel ray approximation and conclude that it can not be ignored for elevation determination through satellite radar system. Meanwhile, I also derive a formula of flattened interferometric phase which verifies that the approximation error can be canceled by removing the contribution to the interferometric phase due to the reference surface.I analyze the statistic characteristics of SAR signals and interferometric phases and the relation between PDF and coherence and multilook numbers which reflects the impact of noise to interferogram under different multilook. The result is help to assess the quality of interferogram and eliminate errors.In the work, I attempt the differential interferometry using 3 ERS-2 C-band images, which were acquired over the tectonically active area of Taiwan where the 1999 Chi-Chi earthquake accured. The errors existed in the interferogram were analyzed and the orbit residual is removed by GPS observations.The slip of the Chelungpu fault triggered of the Chi-Chi Taiwan earthquake (Mw=7.6) which caused a 100-km-long surface rupture that trends north-south. I reconstruct the fault geometry using 1068 planar triangular dislocation elements which better approximate the realistic curved three-dimensional fault surfaces and perform the slip inversion with the observed GPS coseismic displacements as well as InSAR data. The inverting results show that smooth 3D fault model has improved the fit to the geodetic data. By combined inversion of the GPS and InSAR data, we find...