The Genetic Algorithm Of Stress Tensor Inversion And Its Application

With the increase of seismic stations and the improvement of monitoring capacity,more and more seismic records have been accumulated.The focal mechanism estimated form seismic wave describes the sliding mode of source fault.It is important and even the only data source for the study of tectonic stress states in the middle and deep crust.In order to obtain the regional tectonic stress tensor accurately and quickly,the strategy of stress tensor inversion using genetic algorithm based on focal mechanisms is constructed in this paper.The theory is introduced in detail.We analyzed the influence to inverted result under constraint of direction deviation between shear stress and slippage on fault plane,and neglect the shear stress magnitude deviation.The result indicates that we can obtain the correct result only under constraint of direction deviation between shear stress and slippage.The method is tested using synthetic data produced by different stress state with different noisy.We compare the result with another result obtained by grid search algorithm.It indicates that the misfit of results obtained by the genetic algorithm are all smaller than those of results obtained by grid search algorithm.And the difference of misfit obtained by the two method is small,which reflects the robustness of the method in this paper.We apply this method to northeast edge of Tibetan Plateau(103°?106°E,34.5°?37.5°N).The result shows that the region is mainly controlled by near east-west compression from Tibetan Plateau,which caused extensional action towards Alxa block and South China block.The extensional action towards South China block is stronger than that towards Alxa block.