Extracting Coseismic Deformation Field Related To The 5.12 Wenchuan Earthquake By ALOS DInSAR And Numerical Modeling Of The Deformation

This thesis presents a study of a devastating earthquake—Wenchuan earthquake, which happened in the mainland of China in 2008, using both the SAR data and GPS data. Two theories and technologies are combined in order to conduct the research, including modern space geodetic techniques—DInSAR (Differential Interferometry Synthetic Aperture Radar) and the Okada elastic half-space dislocation theory (the geophysical dislocation theory).We computed the coseismic deformation field with spatial resolution of 15m in an area of about 83194 km2, and estimated the optimal epicenter parameters of the one-segment fault model for Wenchuan earthquake.Synthetic aperture radar interferometry (InSAR) is a new radar-remote sense technique developed quickly since 1990's. Differential Interferometry Synthetic Aperture Radar (DInSAR) is a main profile of InSAR application. Since 1990's, DInSAR technology has been popular in geoscience field. DInSAR can be used to monitor very small movement over a large area, which surveyors do not need to enter for investigation on the spot. Compared to the global positioning system (GPS) and the traditional leveling technique, DInSAR has many advantages and good prospects.The article reviews the basic concepts of radar imaging (including the real aperture radar imaging and synthetic aperture radar imaging principle), InSAR, DInAR and introduces the detail steps of DInSAR data processing on GAMMA, which is run on the Linux operating system. This paper employs the two-pass DInSAR method for analyzing the distribution and characteristics of the ground displacement due to the main shock with 23 pairs data of the ALOS satellite PALSAR L-band SAR images, CGIAR-CSI SRTM V4 90m DEM and GPS data. Mainly using the GAMMA InSAR software processing platform to process, we obtain a series of interference results, including SAR magnitude images, interference images, coherence images, differential interferogram and deformation field along the radar line of sight, etc., in Wenchuan earthquake area and the surrounding area of about 83194 km2.In order to ensure the unwrapping reliability, in the DInSAR data processing, we use the method which is to join the GPS control points with the block unwrapping method. In this way, not only the differential interference results can be corrected, but also the initial deformation of unwrapping can not be lost. To obtain the continuous deformation field, in the overlapping region of sub-blocks and different tracks, this paper mosaics the deformation images with a weighted feather method. These two treatment attempts have been made in good results and beneficial to improve the accuracy of the results.But geophysical scholars are concerned with calculating the epicenter parameters from the earthquake deformation field. During the co-seismic deformation analysis, application of the Okada elastic half-space dislocation model is very mature. Based on the results of the DInSAR, this paper simulates the co-seismic deformation field of Wenchuan earthquake using RNGCHN program, which is based on Okada elastic half-space dislocation theory. We determine the optimal epicenter parameters of the one-segment fault model for Wenchuan earthquake, and on this basis, simulate the coseismic deformation in the east, north, vertical and LOS directions. Finally, we compare the DInSAR results and simulate deformation in the LOS direction.