Numerical Simulation For Displacement Of Crustal Movement In Tibetan Plateau And Stress, Strain Analysis Constrained By GPS Data

The movement and deformation of the crust are the comprehensive effects of various kinds of the geodynamical processes on the ground, and the systematical response of the crustal medium to the plate tectonic and deeply dynamic evolution. Therefore, the research for them becomes one of important contents in the geodynamic studies. The characteristics of the movement and deformation of the crust were traditionally determined with the geological and seismographic methods. However, the result obtained with the geological and seismographic methods is virtually an average one on the time scale of millions and/or hundreds of years, and the current movement and deformation of the crust cannot be described well. Fortunately, the modern geodetic measurements such as the Global Positioning System (GPS) technique can overcome the shortage of the geological and seismographic methods in the time dimension; and yet, the coverage of the geodetic survey stations is not sufficient. As a result, it is necessary to employ numerical simulation to investigate the continuous deformation of the crust.The principles of the finite-element method and the general process of the finite-element analysis in the elastic mechanics are simply introduced at first hi this thesis. The finite-element software, called the ANSYS, is used to simulate the displacement, stress and strain fields of the crustal movement in the Tibetan Plateau and its near region with the boundary constraint of the GPS observations. Moreover, the choice of the boundaries, introduction of the faults and generation of the meshes have been improved while creating the model. The numerical results obtained in this study are closed accordance with the other corresponding results obtained by some authors. It implies that the model and the numerical results are reasonable and reliable.Based on the numerical results, the present characteristics of the tectonic stress field in the Tibetan Plateau and the rate of left-lateral slip of the Altyn Tagh fault are primarily discussed in this thesis. From the figure of the simulated stress field, it is found that the east-west or nearly east-west tensile stress is dominant in the Tibetan Plateau, especially on the Himalaya block. This characteristic is explained with three stress fields, which are generated by combined actions of the Indian and Eurasia plate collision, the regional upper mantle convection and the giant gravitational potentialenergy. It is suggested that the current stress field in the Tibetan plateau is a result of the combined actions of various kinds of dynamic evolution. From the simulated displacement field, the left-lateral strike-slip rate on the Altyn Tagh fault is evaluated as about 8mm/a, which accords with the one predicted by the dynamic model that tries to explain the contract and absorbency of the crutal substance in the plateau. It shows that the dynamic model may be dominant to the crustal movement and deformation in the Tibetan plateau today.