Genetic Algorithm-Finite Element Inversion of Topographic Spreading Forces and Drag Forces of Lower Crust to Upper Crust in Tibetan Plateau
ZHU Shoubiao 1) SHI Yaolin 2) ( 1)Department of geophysics, School of Earth and Space Sciences, Peking University, Beijing, 100871; 2) Key lab of calculation geodynamics, Graduate School, Chinese Academy of Sciences, Beijing, 100039)
Based on the data of focal mechanism, the boundary forces, topographic spreading forces and shear forces applied beneath the upper crust are inversed by pseudo-3D genetic algorithm finite element method (GA-FEM) in Tibetan Plateau (72°E-105°E,25°N-41°N). The inversion method of topographic spreading forces is analyzed, and reliable result is obtained. The result shows that the collision between India and Eurasia plates plays a dominant role in forming the stress field in Tibetan Plateau, basal drag forces applied by the lower crust to the upper crust and topographic spreading forces on the margin of Tibetan plateau are also significant factors in forming the stress field. However, significant shear forces are not found beneath the area in Tarim and Qaidam basins. The model displacements inversed from stress field agree with present displacements measured by GPS, showing the result is reasonable, and the present tectonic movement reflected by GPS inherits the long period trend of geological movements.