Simulation Study On Stress Field Of Chinese Mainland Under The Action Of Asthenosphere

The study of the crustal background stress field is one of the important contents of the dynamics research of the Chinese mainland.It is the basic research work carried out by the geomechanics research and the geotechnical engineering.It is also of great significance for the discussion of the earthquake incubation mechanism.The Chinese mainland is located in the southeast of the Eurasian plate and is an important part of the Eurasian plate.Affected by the action of the surrounding plates,modern tectonic movements and deformations are intense and diverse.Since the last century,from the theory of continental drift to the theory of seafloor expansion,and later to the theory of plate tectonics and mantle plume,researchers have gradually focused their attention on rocks while exploring the dynamic mechanism and force source of lithospheric motion On the bottom border of the circle.As the asthenosphere is the structural layer of the lower part of the lithosphere,its influence on the crustal stress field is worthy of further discussion.Starting from two asthenosphere action modes,this paper calculates the crustal stress field of the Chinese mainland under the influence of the asthenosphere through the establishment of a two-dimensional theoretical model and a numerical model of the Chinese mainland,and analyzes the results based on the measured stress data.First of all,based on the current domestic and international understanding of the asthenosphere,this article summarizes two asthenosphere action modes:push-slip action mode and drag action mode.By controlling the relative movement speed of the upper and lower structural layers,different two-dimensional models have been constructed.Comparing and analyzing the calculation results,it is found that:(1)Moho surface and LAB surface fluctuations have a greater impact on the surface deformation.(2)The difference of physical property parameters has a greater influence on deep stress(3)Push-slip boundary conditions can better fit the mechanical state of the asthenosphere.With reference to the analysis conclusions of the two-dimensional theoretical model,combined with the work experience of predecessors,the power exponential law rheological equation and velocity boundary conditions are adopted,and the fluctuations of the Moho and LAB surfaces are considered,and the push-slip motion of the lithosphere on the asthenosphere is adopted.Model,established a numerical model of the Chinese mainland,and calculated the crustal stress field of the Chinese mainland affected by the asthenosphere.Analyze the calculation results of the numerical model of the Chinese mainland:(1)The direction of the maximum horizontal principal stress is centered on the Qinghai-Tibet Plateau and rotates in different directions to the north and west.The stress directions in Sichuan-Yunnan,South China and North China are NW and NWW directions;Xinjiang is NE and NEE directions;Northeast China is NW and NS directions.(2)The maximum horizontal stress values of the shallow part and the deep part have different distribution characteristics.The shallow Qinghai-Tibet Plateau presents the smallest stress level,and the stress distribution within the block is uneven.The Tarim Basin and Tianshan area in Xinjiang show the largest compressive stress.In the deep part,the area of maximum stress is concentrated in the Qinghai-Tibet block,and the gradient of stress change in the area is large.The Western Region block still has a relatively high stress level,but the stress fluctuation within the region becomes smaller.The north-south seismic zone has larger compressive stress in the shallow part than on the east and west sides,but there is no obvious difference in the deep part.(3)The fluctuation of the Moho surface and the LAB surface makes the gravity distribution uneven.The model results are greatly affected by gravity and physical parameters.Different plots have different stress gradients with depth.The in-situ stress field of the Chinese mainland is the result of the geological evolution and tectonic activity of the entire lithosphere over hundreds of millions of years,and is controlled to varying degrees by factors such as plate tectonic pattern,deep material activity,continental internal activity,fault zone distribution,topography and geomorphology.The current stress field in mainland China is only a state in the long-term evolution of the in-situ stress field.The crustal stress field in the mainland China simulated in this paper provides a quantitative reference model for the study of regional stress and tectonic activity.