| The preparation and occurrence of geological disasters’s are essentially the inevitable results of the sudden or slow released by crustal stress-strain that accumulate gradually. In this process, the surface of lithosphere will show deform information with certain form and magnitude. Therefore, access to deform information is the direct way to recognize the geological disasters, while the geodetic is the effective means to obtain the crustal deform information. Especially the rapid development of the space geodetic technologies that the representatives of the GPS, InSAR technology, can be more convenient and effective access to obtain high-precision and real-time accurate crustal deform information in wide range, which have become a powerful means to monitoring crustal deformation, geological disasters and geodynamic phenomena.However, from the surface deform information we can only recognize the initial understanding of the crustal deformation and geological disasters, only by means of surface deformation phenomenon combine with other knowledge to research the internal factors, can we truly recgonize the nature of problems, which is also the essence of geodetic inversion research. But now there are still many critical issues remain to be further refined or resolved in using space geodetic data to do inversion research, including(1) The geodetic inversion research in some particular geological hazards (eg, cracks) is almost empty (2) There are still exist where remains to be improved in inversion theory model and algorithms of deformation (3) There are still more researches need to done in the integrated interpretion on formation mechanism of geological disasters.Therefore, the author selected the Fen-Wei basin which have intense crustal deformation, frequent geological disasters, especially the most frequent and typical ground fissures disaster in China, to in-depth carry out the theory and experiment research on regional crustal deformation, the inversion theroy model and algorithms of deformation, the inherent relationship between tectonic activities and geological hazards, especially the inversion of present tectonic activities feature of cracks and the formation mechanism explanation for geological disasters. The main contents and conclusions of this paper are shown as follows:The present crustal movement velocity fields of Fen-Wei basin and its key areas were obtained based on the GPS observations of "China Crustal Movement Observation Network","Digital Earthquake Observation Network" and "Shaanxi GPS network". Based on those high-precision observations results, the methods of establishing the function relation between surface deformation and crustal stress-strain parameters were mainly studied, such as the graphic element strain, finite element dynamic and elastic plate motion model. The deformation analysis models were constructed which respectively were fit for reflecting the Fenhe basin, Weihe basin and the whole Fen-Wei basin and its surrounding blocks by series of hypothesis test of unbiasedness, effectiveness, applicability, the credibility of the assumptions of models and the significant of parameters. According to the solution results of those models, the characteristic parameters of regional crustal stress-strain were obtained, and the internal relationship between those characteristic parameters and geological disaster was also analyzed.In addition, the author has also utilized the "two-step inversion algorithm" based on InSAR observations, that is, the author utilized Particle Swarm Optimization combined with Monte Carlo simplex nonlinear and Laplace smoothing line inversion algorithm respectively to establish uniform and optimal distributed slip model of seismogenic fault based on elastic half-space dislocation theory. The accuracy assessment were also done to the inversion parameters and the uncertainty of the distributed slip model. Then take the New Zealand Fiordland7.8Mw earthquake for example, the author used the "two-step inversion algorithm" mentioned above to obtain the precise source parameters information of the earthquake. And the "co-seismic dislocation" theory,"double dislocation" theory model which is established based on genetic search algorithm were used to the inversion study of ground fissures activities parameters, obtaining the activities parameters of Xi’an, Qingxu crakes and their relationship with the fault activities.Finally, the internal and external coupling dynamic formation mechanism of Xi’an, Datong. Qingxu typical cracks were comprehensive explained combined with the geodetic inversion results of this paper, tectonic, earthquake activity, groundwater extraction factors and so on.Through the above theory analysis and plenty of examples, the main conclusions and innovation results were obtained as follows: 1. The present crustal stress-strain characteristic parameters of Fen-Wei basin were obtained by establishing the function relation model between GPS deformation and the crustal stress-strain parameters, such as the graphic element strain, finite element dynamic and elastic plate motion model. The results show that the stress-strain parameters of Fen-Wei basin mainly present tension stress-strain with NW-SE direction, the magnitude of principal stress-strain parameters are between10-4～10-3kPa/y and10-8～10-6/y respectively. And those results quantitatively confirmed that the whole Fen-Wei basin presents extensional mode.2. The internal relations between regional crustal stress characteristics parameters and cracks disaster was proclaimed for the first time according to the results of space geodesy inversion. All of the cracks-prone areas within Fen-Wei baisn present notable tension stress-strain volumes, and the direction of which is approximately vertical to the development direction of ground fissures, thus revealing the regional tectonic tension stress field of NW-SE direction is the power source of cracks development in Fen-Wei basin.3. By solving the deformation analysis models which respectively suitable for reflecting the whole Fen-Wei basin and its surrounding blocks, the results show that the Ordos, south China, Hetao, Yinshan blocks have the characteristics of rigid deformation, while the Weihe basin, Taiyuan-Xinzhou basin, Datong basin, North China and other blocks have the characteristics of non-linear deformation. Hence, those inversion results can quantitatively prove that the whole Fen-Wei basin and its surrounding blocks have different characteristics of tectonic activity.4. The "co-seismic dislocation" analysis theory was used to the inversion study of ground fissures activities parameters for the first time. And the fine segmentation, stratification, lateral uneven activity characteristic of cracks and its internal relationship with tectonic fault activities were obtained. So some new understanding for ground fissures activities are obtained based on the above geodetic inversion results.5. Combined with the internal and external coupling dynamic influencing factors of the ground fissures and the geodetic inversion results systematically and comprehensively, the author integrated analyzes the formation mechanism of the development and activities of typical ground fissures within Fen-Wei basin based on the tectonic backgrounds of cracks formation, the geology tectonic conditions of cracks development and the external precipitating factors that affected the cracking and unnormal activities of ground fissures. |
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