Coseismic Deformation Derivation And Source Parameters Inversion Based On InSAR

Among all natural disasters, earthquake is thought of the most severe one, which can cause severe damage of the earth surface, and serious losses of life and property. After long-term research on the earthquake, it has been proved that the crust movements cause, as the stress accumulation increasing, the fault will eventually slip and casue an earthquake, which will produce the deformation on the surface. If the fault slip were revealed by the geodetic observation data, the results can be used for the earthquake simulation and prediction and it will be very important practical significance for the seismic disaster reduction. Synthetic aperture radar interferometry (InSAR) is a new geodetic technology developed in the past30years. It is very suitable for seismic deformation observation due to the features of detecting large area surface deformation caused by earthquakes. Using the coseismic deformation measured by InSAR, the coseismic slip distribution of causative fault can be solved by inversed method. The main contents of this thesis are to introduce the InSAR fundamental and analyse the error sources of D-InSAR deformation, obtain surface coseismic3D deformation including abundant information, and get the slip distribution of two exampled earthquakes with actual methods. The key research contents and innovations in this thesis are outlined as follows:1) The surface coseismic three dimensional (3D) deformation of L'Aquila earthquake was calculated by two steps from the data of different platforms and different orbits. The element task is to resample the different data to the same format, which can make all the data have the same resolution and all the pixels of different data have the one-to-one relationship. According to the radar imaging geometry relationship, the initial3D deformation was calculated at first; then the easting and up deformation was calculated without considering the contribution of northing deformation for the second time. Combining the initial northing deformation with the second time easting and up deformation as the final result, the final3D deformation data was compared with seventeen GPS sites deformation in this area and the results showed that the calculated3D coseismic deformation is highly accurate and reliable.2) Systematic and quantitative analysis of the medium layered influences was carried out when simulating the coseismic deformation, the results showed that the impact of layered media should be considered during deformation simulation and inversion within some special seismic magnitudes and geodetic data. During the experiment, the parameters of different magnitude and different fault structure were calculated by empirical formula, then the3D surface deformation and ASAR ascending orbit LOS deformation caused by the fault slip based on uniform model and layered model were simulated respectively. By analysing the differences between these two models, the influences were estimated and some conclusions were drawn, the conclusions include that the medium layered effects need to be considered when the impact of layered media can be detected by GPS and InSAR.3) Coseismic deformation of Yushu earthquake was calculated using PALSAR data, and the inversion of slip distribution was derived from the coseismic deformation, the slip distribution showed that the fault mainly is a left-lateral fault. Before inversion, the phase ramps of orbit errors were removed from the differential interferogram of PALSAR data using polynomial model based on least-squares method, then the coseismic deformation was obtained. By considering the actual geolocial surveys and the3D deformation characteristics, the geometric parameters were determined and the fault was divided into five sections. Based on the finite elastic uniform half-space model, the coseismic fault slip distribution was inversed using the least-squares method, the total moment is3.4x1019Nm (Mw7.0), which is consistent with the USGS result. The Monte Carlo simulation method was employed to estimate the uncertainty of the inversed results, and the slip on suface was compared with the geological surface offset of fault, all these showed that the slip distribution is reliable.4) GPS and InSAR deformation data were used as the fitting targets, the fault slip distribution of L'Aquila earthquake was calculated by two steps, the fault is a normal fault with slight right-lateral slip. The first step is non-linear inversion, which is carried out using the genetic algorithm to determine the geometric parameters of the fault. With the analysis of3D coseismic deformtaion and the geological background data, the parameters of strike, length, dip and dip slip were set to small searching ranges, this increased the efficency. The second step is linear inversion, which is performed to obtain the fault slip distribution by steepest descent method with the smoothness constraint, the result showed that the total moment3.3×1018Nm (Mw6.3) bigger and closer to the USGS result than the one calculted based on uniform model by previous researchers.