Study On Inversion Of Regional Tectonic Stress Field And Models Based On Geodesy Data

Inversing the tectonic press field by using geodetic observation information is one of the most popular topics in Geodesy inversion over the recent years. According to the gravity tectonic movement theory, this thesis intensive studies the tectonic press field and the models based on the modern geodetic observation data, and the research results is validated in North China. Main research contents as follows:(1) Discusses the Geodesy inverse problems related to the Geodynamics research. Gives out problems as well as solutions of norm minimization, over-determined, and mixed which including both minimization and over-determined. Studies three kinds of Geodesy inverse models, that is what based on Dislocation mode, solid mechanics mode and jointly inversion mode. Studies Geodesy inversion methods and especially focuses on the GPS displacement inversion method. Introduces common calculating methods in Geodesy inversion, emphasizes on the finite element method.(2) Studies the Gravity tectonic mechanism, comprehensively and systematically analyzes tectonic movement mechanism caused by Gravity of the earth, based on summary of existing theories and viewpoints. Discuss the calculating method of the Gravity tectonic press field.(3) On the basis of Gravity tectonic field calculating method which infinite plane ban hypotheses, studies calculating Gravity tectonic field method which based on sphere shell hypothesis. Based on the function formula between the Gravity tectonic field and vertical line deviation, calculate complete and incomplete Gravity total level grads, Bouguer Gravity anomaly and vertical line deviation in North China respectively with 1:1,000,000 30'×30'DTM digital terrain model of China mainland,360 rank Gravity field model EGM96 and Eigen-GL04C model. Figure out the tectonic stress models of the different strata in North China respectively. Comparative analyses between this thesis results and previous research results, several helpful conclusions are as follows:It's potential that calculate the Gravity anomaly and the deviation of vertical line in any area by using Gravity model, high-resolution DTM model and related software. Application Bug Gravity anomaly and vertical line deviation to obtain regional tectonic stress field corresponding to existing geological and seismic data. There are both advantages and disadvantages in obtaining the tectonic stress information, so it's necessary to consider the advantages and disadvantages of these two approaches synthetically, in order to work out better explanation and forecast of the crustal movement. The total horizontal Gravity gradient and tectonic stress in North China can reflect the interaction between the blocks and the structure's character of the crustal, the structure's activity can be interpreted from the strength or weakness of the tectonic stress field.(4) Studies the anomaly relation between Gravity tectonic stress field and density, calculates the value of gravity anomalyΔg and geoidal height N using 360 steps EGM96 model and DTM digital terrain model of China mainland, and applied the model to the research area of [10°-60°N,79°～140°E], calculates the value of density anomaly and average tectonic stress where 20～25 kilometers,25～32klimeters and 32～36klimeters deep underground. Gives several helpful conclusions by analyzing the calculated results are as follows:The tectonic stress and the density anomaly corresponded closely; the density anomaly change is larger where the tectonic stress change greater, leading to increased crustal movement in that region. The tectonic stress is related to the depth of the stratum, the tectonic stress increases greater when the stratum is deeper if the density anomaly unchanged.(5) Studies related Geodynamics problems in North China by using finite element arithmetic method. Analyze the main factors which affect the precision of inversing, including the perfection of geographical model, distribution of geodesy observation points and the value of stratigraphy-physical parameter and so on. Probed the tectonic fault, stratigraphy-physical and other parameters in North China, and partitioned the research area and obtain the prior information about parameters. Build the spatial linear-elastic model according to the ideal of the finite element method. This thesis studies the Geodynamic inversion problems by using the rock actual Gravity of the research area, experiential numerical value of the rock mechanics medium parameter and boundary press and selected the GPS displacement monitoring points during 2005-2006 in North China as the inversion displacement boundary conditions. At the same time, the rule of least-square is taken in the research. That is to let the summation of square number of the difference between the calculated displacement value and the GPS observation value minimal by repeated adjusting the boundary press and medium parameter. This thesis studies and updates the experience information of press, strain, density of strain energy, boundary press, and medium parameter and so on. On this basis, gives an explanation to the Geodynamic phenomena of the researched area by the inversion result, and discusses some Geodynamics phenomena and Geodynamic mechanism. Main conclusions are as follows: The direction of the host stress in North China which is constrictive stress field is basically NEE direction. The maximum stress difference in the area is positively related to the strata depth, the maximum stress value is smaller in the center area and bigger around, the deviations is in negative related to the strata depth. Value of the maximum host stress is gradually reduced from the top to the forth strata and it's mainly press stress, tensile stress often exists at the bindery of the top and the second strata. The maximum host stress is generally distributed around in the middle area, at the same time the minimum host stress is mainly to arise at the boundary or inside fault. The reason why the fault occurs is that there accumulates too great stress. The outstanding feature of the host strain in the year 2005-2006 in North China is there is mainly host press strain while host tress stress next. The change of density of strain energy in North China is not obvious compared with density of strain energy before the year 2005-2006, tells that there is little energy accumulated underground.