| Earthquake has a greatest impact on the production of human life, it is the most damagingin all kinds of natural disasters. For a long time study by the seismologists, it has found that theoccurrence and birth of earthquake are usually due to the accumulation of stress in the crustduring crustal movement, when the stress exceeds the critical state causing the dislocation,resulting in a variety of degrees of surface deformation and destruction ultimately. Study ofdislocation using deformation observed by geodetic techniques can be used to study faultdislocation, and as the basis of earthquake simulation and earthquake prediction, it has a veryimportant practical significance on reducing the impact of earthquakes. Since being introducedto the study of earthquake, space geodesy research develops rapidly and has become one of themost accurate and effective means in earthquake preparation activities.GPS technology can get deformation precision in mm level of any point in the world,through joint measurement densified method, it can grasp the characteristics of fault activitiesaccurately. While the Interferometric Synthetic Aperture Radar (InSAR) is a kind of newtechnology for earth observation during three decades, it can get a wide range of surfacedeformation caused by the earthquake, and is very suitable for seismic deformation monitoring.Using coseismic deformation data acquired by GPS and InSAR can invert the slide ofseismic fault. Based on space geodetic techniques and crustal deformation parameter inversionmethod, this paper is mainly conducting a series of researches on Yushu earthquake. Theresearch content and results including the following aspects:1) Based on improved spherical coordinate system least squares collocation method and blockconcept, surface displacement data calculated by Gamit/Globk is used to obtain the surfacedisplacement, strain, dilation and shear strain rate distribution of Bayankala block andQiangtang block. Results show the strain, dilation and surface shear strain rate exist aunique earthquake signals before the eve of Yushu earthquake. From the macroscopic scale,the strenuous activity of Bayankala and Qiangtang block and the inevitability of Yushuearthquake are certified.2) Based on D-InSAR technique, the coseismic surface deformation displacement distributionin line of sight of Yushu earthquake is acquired. The overall deformation zone is clearly visible from D-InSAR results, it can be judged that Yushu earthquake was seismogenic inGanzi-Yushu-Fenghuoshan Fault, showing the characteristics of left-handed, and there aretwo heavy disaster areas in the earthquake: Yushu county earthquake disaster area andLongbaotan seismic area. Along the Ganzi-Yushu-Fenghuoshan fault, the surfacedeformation of the epicenter in the northeast is along the radar line of sight to uplift; thesurface deformation of epicenter in the southwest is along the radar line of sight to sink.Among them, the maximum coseismic surface deformation area is located in Yushu Countywhich is nearly-0.442m.3) Based on Okada rectangular dislocation model, the underground seismogenic fault ofYushu earthquake is divided into3sub-faults to carry on the parameters nonlinear inversion,on the basis of original InSAR deformation along line of sight, the coseismic surfacedeformation field of Yushu earthquake along line of sight is simulated. And it can beverified that Yushu earthquake is a tectonic earthquake caused by underground fault activity.Through the empirical formula, it can be obtained that the seismic moment of Yushuearthquake is about3.4×l019Nm, the magnitude is about Mw7.0. From the microscopicpoint of view, the validation study on seismic fault tectonic development on the produceearthquake cannot be ignored.4) Based on elastic rebound DefNode negative dislocation model, the rotating Euler pole ofQiangtang block and Bayankala block is calculated. The result shows that, relative toBayankala block, the rate of Euler pole rotation in Qiangtang block is higher in clockwise.On the view of rotation angular rate, the reason of left-strike-slip characteristics in Ganzi-Yushu-Fenghuoshan fracture is interpreted.5) Based on DefNode negative dislocation model, the area closure rate distribution of pre-earthquake seimogenic in Ganzi-Yushu-Fenghuoshan fracture is researched. It can be seenthat, in the southeast of Yushu area, strain energy accumulated relatively quickly under theinfluence of closure rate, gradually accumulated to the limit of fault block level, oncebeyond the limit to overcome the friction of fault blocking effect, the fault ruptures andcauses the occurrence of earthquake activity; in the northwest of Ganzi-Yushu-Fenghuoshan fracture, blocking ratio is relatively small than southeast, it may be connectedwith underground fault on the adjustment of the regional deformation, strain energy absorption and the size of the underground structure produced by the shear friction... |
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