Research On The Geodesy Inversion Mode Considering The Earth Structure And Its Application

Based on the geodetic observation signal with combining the geological, seismic and geophysical data, the aim of geodesy inversion mainly focus on inverting kinematics and geodynamics model parameters, modifying and proposing new geodynamics model using the priori geodynamics model from the geophysical research. It also could be used to invert the movement of active faults and blocks from the surface observation data, discuss the relationship between the crust motion and earthquake and make the prediction and forecast on seismic and geological disaster.In this paper, the split-block and multi-faults joint inversion mode has been firstly constructed by combining the geodesy with active block and seismic fault dislocation model. The co-seismic deformation inversion mode and post-seismic deformation inversion mode considering the earth structure also have been given out after studying the deformation difference due to different earth structure model. The related inversion program has also been developed out and used to study the China strong earthquake areas with GPS observation and make the specific inversion analysis. All the work has been done as below:Generalizing the historic development of the dislocation model in elastic, homogeneous and half space medium and spherical stratified dislocation model in system and comparing the difference between the two types model provide the theory foundation to make inversion formulation. Pointing out that the deformation difference due to the different models could be detected out by observed information with the highly improved precise observation along with the modern geodetic technology development. Relative to the truly spherical layered model, the dislocation model in elastic, homogeneous and half space medium must have taken the model errors because of the hypothesis to the true earth model, which must be considered into the practical use.We developed the split-block and multi-fault joint inversion mode based on the half space, homogeneous and elastic dislocation theory and active block Euler parameters theory considering the rich GPS observation data from the China crust movement-monitoring net. This inversion mode could simultaneously study the block motion in large scale and the fault characteristic in small scale. Jointly using the bootstrap method and statistical model to evaluate the inverted parameters and give the confidence internal. The inversion work had been done to the North China area and Sichuan-Yunnan area respectively to study the active characteristic of blocks and faults and analyze the block movement, fault slip and seismogenic power etc. The inversion results show that each fault has the ability of 5 to 6 equivalent magnitude of potentially earthquake, which suggests us to reinforce the deformation monitoring to the relative active fault.Considering the inhomogeneous, stratified and spherical characteristic of earth structure, the co-seismic deformation deference due to strike slip fault and dip slip fault among spherical earth layering model, spherical homogeneous model and half-space homogeneous model has also been studied in this paper. The affection of the crust layered and earth curve is also discussed in large and little scale region. It could be easily got that the horizontal and vertical deformation difference due to strike slip fault considering the earth structure both are near 10 percent, but the numerical value of vertical deformation is little to ignore in the little scale region, while the horizontal deformation difference is about 20% and vertical deformation difference is more than 20% in largescale region. When to the dip fault, it could easily get that the horizontal deformation difference due to strike slip fault considering the earth structure both is near 10 percent and the vertical deformation is very small to consider in the little scale region, while the horizontal and vertical deformation difference are both about 10% in large scale region. The research to the little scale region shows that the deformation difference is mostly affected by the crust stratified, while the research to the large scale region is mainly affected by the crust stratified too, but obviously reflecting the affection of earth curve. The quantitative deformation difference have also been studied and compared due to the three types model to analyze the affection by each earth model. The calculation results show that the surface co-seismic defonnation difference is so large that exceeding the accuracy of high precise observation technology if not considering the actually earth structure when just taking the earth as half-space homogeneous medium. Finally the co-seismic deformation inversion mode due to seismic fault has been set up considering the earth-stratified structure. Using the nonlinear inversion formulation to make the simulated calculation and inversion analysis to strike slip fault, dip slip fault and tensile fault separately. The inverted results show that the inversion mode could well invert out the fault dislocation parameters and could be better settle down the inversion work to the practical seismic fault co-seismic inversion problem.Post-seismic deformations are investigated on strike-slip, thrust and tensile faulting considering different crustal layering structures in a spherical elastic-viscoelastic earth model. Differences in surface deformation calculated between a homogeneous earth model and stratified earth models are quantitatively compared and discussed in detail. The results show that strike-slip dislocation fault due to the crust medium impact is mainly concentrate on the surface horizontal deformation, when calculating the defonnation difference accumulated after 10 and 15 years', it is up to 10.7mm and 12.4mm in x direction and up to 5.8mm and 6.8mm in y direction respectively. The dip-slip dislocation fault due to the crust medium impact is mainly concentrate on vertical deformation and the vertical defonnation difference is up to 6.7mm and 9.4mm, respectively between homogeneous and layering models after 10 and 15 years' accumulated. The tensile dislocation fault due to the crust medium impact is mainly concentrate on both horizontal and vertical deformation that the horizontal deformation difference in y direction is up to 16.3mm and 20. 3mm separately while vertical deformation difference is up to 6.7mm and 8.9mm respectively between homogeneous and layering models after 10 and 15 years' accumulated. Post-seismic deformation accumulated 28 years after the 1976 Tangshan earthquake have been estimated with the realistic crustal structure from seismic investigation. The horizontal deformation is about 10cm while the vertical defonnation reaches about 7cm. The results show that the maximum difference in horizontal deformation is about 20mm for different crustal models used, while the difference in vertical deformation is about 10mm. These results demonstrate that the distortion in surface deformation caused by ignoring layering properties of crustal structures greatly exceeds the current accuracy of GPS survey (2 mm) and therefore can not be ignored. When using the actual observation data to make inversion analysis, the affection by the crust layered structure must be taken account of in use.Considering the spherical visco-elastic structure, the post-seismic deformation inversion mode had been constructed based on the visco-elastic earth model. We developed the inversion mode and inversion software package based on the post-seismic fault dislocation model considering the crust-stratified structure. Using the genetic algorithm to invert the different faultdislocation parameters due to strike slip fault, dip slip fault and tensile fault respectively and comparing to the result inverted from the homogenous dislocation model, the result shows that the inversion algorithm used here could invert the dislocation parameters from the large region using the genetic algorithm and the inversion result is better to use. The inversion mode proposed here could better invert the seismic source parameters to different types fault. There is also a important find to suggest us that we could not use the minimum of VTPV as the only rule to judge the inversion result whether good or not when the model mode is not obvious. We should find other ways to make a supplement judge.Using the co-seismic deformation inversion mode and post-seismic deformation inversion mode considering the earth structure, the practical inversion application had been done to the Jiashi strong earthquake area during the year 1997 to 1998. The seismic deformation has been studied using the observation data get by about 40 GPS monitoring station in Jiashi and adjacent area from 1994 to 2001, especially focused on co-seismic and post-seismic deformation. Using the proposed inversion mode we have successfully inverted out the seismic fault dislocation parameters, which had broken out on 27th, August 1998. The inversion parameters show that the upper depth fault is about 12.15km and the lower depth of the fault is about 39.89km. The length of fault is about 37.85km and has a slip about 1.09m. The dip angle of the fault is about 52.86 in degree while the strike of the fault is about NE144 in degree. The inversion results present that the fault is a blind fault with a strike direction from North to West and it has crossed from the upper crust to lower crust. The characteristic of the fault is mainly in right strike slip and has a little normal attribute. The inversion result is mainly agreement with the seismic data analysis result by Shan Jianxin in 2002. Based on the geological crust structure data, we also have inverted the visco-elastic characteristic of crust structure in Jiashi area. The inversion result manifests thatvisco medium of lower crust is about 1.8xlO19Pads while that of the upper mantle is about(0.3~3.0)xl018Pali, which shows that the deep mass structure is a strong lower crust overlapping a weak upper mantle that is agreement with the research of Vergnolle in 2003.