| Most of the previous studies on plate motion models based on geological and geophysical data focused on rigid motion model under Euler Theorem,and the results often indicated the average movement of millions of years as a time scale,with inadequate up-to-date state.Rapid development of modern spatial geodetic measure technology and dense placement of GPS monitoring stations facilitate the establishment of high-precision crustal movement models.According to the recent GPS data in the Bohai Rim region by Crustal Movement Observation Network of China,the author establishes models of crustal movement velocity field in the Bohai Rim region by various methods,analyzes the characteristics of crustal movement and deformation in the Bohai Rim region,and shows the main strain figure,surface expansion figure and maximum shear strain figure in the Bohai Rim region.The spatial distribution characteristics of crustal movement in this area are analyzed briefly in this paper.The main contents are as follows:1.Proposal of a new method for detecting and removing anomalous stations by taking into account the intraplate deformation.Specifically,the anomalous stations in the GPS velocity field are eliminated by means of the IGGIII scheme with robust estimation and the combination of the rotation of entire block and linear strain model(RELSM).The new method mainly takes into account the differences between the overall trend(smoothness)and the local structure movement.Compared with the method of judging whether the point is anomalous stations according to the statistics constructed by the rate residuals of the rigid motion model,the new method can be used to get better fitting accuracy of the velocity field.2.The least squares collocation model for crustal deformation analysis is established by using the signal to describe the irregular intraplate deformation of the block.A variance-covariance matrix of crustal deformation analysis is established by using Gaussian function,similar Gaussian function and Hirvonen function as covariance function.The GPS velocity field is fitted by different covariance functions based on the GPS velocity field data in the Bohai Rim region.The results show that the fitting result of the Hirvonen function is best,more suitable for crustal deformation analysis in the Bohai Rim region3.Based on the rigid motion model,rotation of the entire block and homogeneous strain model,rotation of the entire block and linear strain model,least squares collocation model and multi-surface function model,the author established the crustal horizontal movement model in the Bohai Rim region.In this paper,the grid interpolation velocity field of various models is drawn according to the interpolation interval of 0.5~??0.5~?.The fitting and estimating results show little difference between the rate of fitting and estimation of the five models and the actual observation results,which indicates that the overall crustal movement of the region has long-term stability;the trend is the main;the intraplate deformation is not significant for the difference of various models in the overall fitting.4.According to the rotation of the entire block and linear strain model to calculate the strain parameters,the main strain of each point is calculated at the interpolation interval of 0.5~??0.5~?,and the main strain figure,the surface expansion strain figure and the maximum shear strain figure of the Bohai Rim region are drawn.The analysis of the strain figure shows that the principal tensile strain at the north of38~?Nis greater than the principal compressive strain,which is the expansion movement,and the principal compressive strain at the south of 38~?Nis greater than the principal tensile strain,which is the compression movement.Stronger geological tectonic movement happens in the southwest and northeast regions,weaker in the northwest regions.In general,the whole region is in a state of weak expansion,which is generally consistent with the existing geological conclusions. |
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