The Resolving Methods For The 3D Coseismic Deformation Field Based On The Multi-LOS DInSAR Technology And Applications

The Dfferential Interferometry Synthetic Aperture Radar (DInSAR) technology is one very important method to monitor earthquake deformation. One of its limitations is that an interferogram only measurementss one component of the surface deformation—in the satellite's line of sight (LOS), but not the real surface deformation in the vertical and horizontal directions, and this question is named"LOS Amphibious". In order to overcome this question, based on the Multi-LOS DInSAR technology, this thesis firstly suggests 4 solutions: the model of direct solution, the model of combining the simulation method, the model of combining the offsets method, and the model of projecting GPS measurement to LOS direction. The former three solutions can be used to calculate the three-dimensional (3D) deformation field, which belong to the forward-model. The fourth solution uses the GPS measurements to calculate their LOS deformation, and can be used to inspect and evaluate the accuracy of the coseismic interference deformation field, which belongs to the backward-model. Then, this thesis chooses the Gaize earthquake, Yutian earthquake, Bam earthquake and Wenchuan earthquake to evaluate the advantages and disadvantages of the four models. Finally, this work obtains the 3D coseismic deformation fields of Gaize earthquake, Yutian earthquake and Bam earthquake, respectively, and the coseismic deformation field and precision evaluation of the Wenchuan earthquake. By the characteristic analysis of the Multi-LOS and 3D coseismic deformation fields, this work gives the rupture modes of the four earthquakes, respectively.[1]Four solutions to the problem of DInSAR LOS AmphibiousThe model of direct solution: It uses the coseismic deformation fields of three different LOS directions to set up the solution model of 3D deformation for calculating the 3D coseismic deformation field. It has higher reliability, and avoids the uncertainty of simulation or assumption methods. But, it is usually very difficult to obtain the coseismic deformation field in different LOS directions, and the solution precision of the north-south direction is uncertain.The model of combining the simulation method: Using coseismic deformation fields of ascending-orbit and descending-orbit modes in two different LOS directions, and the simulated NS direction coseismic deformation field, it constructs the 3D deformation solution model for calculating the 3D coseismic deformation field. Its advantage is to use the simulation value to replace the measured value, which reduces the requirement of observation data. But the simulated deformation fields are inevitably different to the actual, and the different fault modes can produce various simulative results.The model of combining the offsets method: Using coseismic deformation field of ascending orbit and descending orbit modes in two different azimuth directions by offsets measurements, and the coseismic deformation field of ascending orbit and descending orbit modes in two different LOS directions by DInSAR, it sets up the 3D deformation solution model for calculating the 3D coseismic deformation field. Its advantage is to use the azimuth coseismic deformation field to resolve the 3D deformation, which reduces the requirement of observation data also. Furthermore, the calculation precision of this method is better than the pure offsets way, especially in vertical and east-west directions. The pure offsets method seems more appropriate to calculate the north-south direction deformation field, and the combining offsets method is more advantageous to calculate direction deformation fields in vertical and east-west direction.The model of projecting GPS measurements to LOS direction: It projects the GPS measurements of 3D coseismic deformation value to InSAR LOS direction by projection mode, and compares the projection result with DInSAR measurements in order to validate and evaluate the accuracy of the coseismic interference deformation field. Its advantage is to combine the GPS with DInSAR measurements to analyze the characteristics of coseismic deformation. But there are some deviations between the GPS and DInSAR measurements because of the different spatio-temporal scales of the two methods.[2]The 3D coseismic deformation fields of typical strong earthquakes calculated based on the 3D resolving modes, combined with Multi-LOS DInSAR technologyIn order to overcome the"LOS Amphibious"of interferometry, this thesis proposes the four resolving methods: the model of direct solution, the model of the combining simulation method, the model of combining the offsets method, and the model of projecting GPS measurements to LOS direction. And the 3D coseismic deformation fields are calculated based on the former three solutions, which construct the 3D resolving equation using the Multi-LOS interferometry, simulated and offsets results. And then, three 3D coseismic deformation fields of typical strong earthquakes are obtained, i.e. Gaize earthquake, Yutian earthquake and Bam earthquake.[3]Combining the GPS with DInSAR to evaluate and revise the coseismic deformation field of Wenchuan earthquake, based on the model of projecting GPS measurements to LOS direction.This work uses the 3D coseismic deformation measurements of twenty-six GPS stations to evaluate the precision of Wenchuan coseismic deformation field, based on the model of projecting GPS measurements to LOS direction. The evaluation result shows that the seismic deformation characteristics shown by the GPS and D-InSAR are coincident. Because of linear characteristics of the atmospheric delay error of L-band interferometry, the DInSAR result is corrected by the linear regression analysis of the GPS and DInSAR result, and the average absolute deviation between the GPS and DInSAR measurements is reduced from 15.2 cm to 4.9 cm.[4]On the deviation between GPS and DInSAR measurements of Wenchuan earthquakeThe deviation between the GPS and DInSAR measurements probably comes from several aspects: 1.The first is the difference of time scales, as the coseismic GPS measurementss were close to the shock time, but the coseismic interference measurements were much different from the shock time, and the earliest ALOS satellite data of aftershocks was a week later than the shock time; 2.The second is the error influence of measurements, which refers to the vertical deformation error of GPS measurements and the atmosphere delay error of L-band DInSAR measurements; 3.The third is the difference of spatial scales. The deformation value of GPS measurements were observed at the GPS cites, but the deformation values of interference measurements were derived from the pixels of SAR images; 4.The last is the difference of reference systems. GPS measurements usually are referred to the Eurasia system, but the DInSAR measurements are referred to the unwrapped points. Just because of these influences, the results of GPS and DInSAR measurements which have caused the LOS projection of GPS measurements to be smaller than the DInSAR measurements of Wenchuan coseismic deformation.[5]Insights of coseismic deformation field and thrusting rupture of the Wenchuan earthquakeThe characteristic analysis of the Wenchuan coseismic deformation field shows that the coseismic deformation field can be divided into northwest part (hanging wall)and southeast part (foot wall) by the NE-striking seismic rupture; and the northwest part, Bayankala block of Tibet is subsiding mostly in the LOS direction; whereas the southeast part, Sichuan basin is uplifting mostly in the LOS direction.The northwest part Bayankala block and southeast part Sichuan basin collided each other strongly during the Wenchuan quake, and mainly ruptured by thrusting with right-lateral striking component. When the Bayankala block thrust upwards along the sesmic ruptures, it also moved to the east to overlay the Sichuan basin, under the huge push power eastward. And because of the far distance of LOS direction caused by its eastward movement and right-lateral striking larger than the shortening distance caused by its uplifting movement, the Bayankala block shows subsiding characteristic in the LOS direction. When the Sichuan basin thrust downwards along the seismic ruptures to obstruct eastward movement of the Bayankala block, it also moved to west below the Bayankala block. And because of the shortening distance of LOS direction caused by its westward movement and right-lateral striking larger than the far distance caused by its subsiding movement, the Sichuan basin shows uplifting characteristic in the LOS direction.[6]The seismic rupture modes of typical strong earthquakes derived from the characteristic analysis of 3D coseismic deformation fields①3D coseismic deformation field characteristics and double-quake rupture mode of the Gaize earthquake.The characteristic analysis of the 3D coseismic deformation field of the Gaize event shows that the northwest wall of the eastern fault(NNE striking and NW dipping) caused by the Mw6.4 mainshock moved downward and toward to south, and east; The northwest wall of western fault (NNE striking and NW dipping) caused by the Mw5.9 aftershock moved toward to depth, north, and west. According to the characteristic analysis and 3D display, the rupture process of the Gaize earthquake is: tensile stress accumulation in the step position(left step) of left-lateral striking fault of the Gaize-Dongcuo fault and Yibucaka-Riganpeicuo fault maybe had caused the twice normal ruptures along NNE direction. The Mw6.4 mainshock was mainly ruptured by normal and left-lateral striking, with a little rotation to east; and the Mw5.9 aftershock was mainly ruptured by normal faulting, with a little right-lateral striking.②Yutian 3D coseismic deformation field characteristic and rupture mode of three-segments normal faulting with left-lateral striking.The seismogenic fault of Yutian earthquake can be divided into three-segments, which are north section of No.1, middle section of No.2 and south section of No.3, respectively. The 3D coseismic deformation field shows that the western wall (hanging wall) of the three-segment fault moved down overall, whereas the eastern wall uplifted; the western wall of the No.1 and No.3 faults moved toward to west, whereas the western wall especially nearby to the No.2 fault moved toward to east, and all the eastern wall of the three-segments moved toward to east (dE); the western wall of the No.1 and No.2 faults moved toward to south, whereas their eastern wall moved toward to north, and both the western and eastern wall of No.3 fault moved toward to south(dN). By the comprehensive analysis of the 3D coseismic deformation field, simulated deformation field and 3D display, the seismic rupture mode of Yutian earthquake is: the three-segment faults of the Yutian earthquake are mainly ruptured by normal faulting and left-lateral striking, and spatial distribution of the three-segment faults is featured by left step en echelon.③3D coseismic deformation field characteristic and rupture mode of dominant right-lateral striking, with a little left-lateral horizontal rotation in the east-west direction of the Bam event.The seismogent fault of the Bam earthquake is nearly north-south striking, and the coseismic deformation field can be divided into four quadrants. The characteristic analysis of the 3D coseismic deformation field shows that the northwest quadrant uplifted and moved to north and west; the northeast quadrant moved down, to south and west; the southeast quadrant moved toward to up, and to south and east; the southwest quadrant was losed during 3D solution. According to the characteristics analysis and 3D display, the rupture mode of Bam earthquake is: under the principal tensile stress of northwest and southeast direction, the Bam earthquake was ruptured mainly by right-lateral striking mechanism, with a little left-lateral horizontal rotation in the east-west direction.[7]?Primary applicability of the four models determined through comparing and analyzing of the advantages and disadvantages,。By computing the deformation in the vertical direction (dU) and east-west direction (dE), the mode of direct solution is preferred, the model of combining the simulation method is the next choice, and the model of combining the offsets method is the last choice; whereas, for computing the deformation in the north-south direction (dN), the model of combining the simulation method is best of all, the next is the model of combining the offsets method, and the last is the model of direct solution. Based on the advantages, disadvantages and characteristics of the models and arithmetic, this articles sums up the primary applicability of the four models according to the strikes and rupture mechanisms of seismic faults. The analysis result of advantages, disadvantages and applicability is beneficial to resolving the 3D deformation field and evaluating the precision of interference deformation field in the future.