Study Of Regional Crustal Deformation Of Geodetic Data

The movement and deformation of the crust are directly or indirectly related to the environment for human survival, climate change, earthquakes, and volcanic eruptions. It is scientifically meaningful to study the crustal movement in China’s western region for understanding climate change and predicting natural disasters in current China. Space geodetic measurement is one of the major means for monitoring crustal movement and deformation. The satellite gravity survey is a new method for the study of crustal deformation owing to its advantages of higher global coverage, observation points free of control of natural conditions, and observed results free of influence of ground position changes. In this work, the crustal deformation and the fault activity in China’s western region were calculated by satellite gravity data and GPS data, on the basis of which major achievements are involved in:1. The earth density stratified model was then used to calculate the crustal thickness distribution in the mainland China. The crustal thickness distribution was verified Using GRACE (Gravity Recovery and Climate Experiment) data. The results were accord with that achieved by reference [66].2. The seismic gravity variation of Ms8.0earthquake at Wenchuan of China was computed by GRACE data. The variation value was about-3×10-8ms-2, which was interpreted by the earth’s crust expansion model and the dislocation theory.3. The standard PSO algorithm (Particle Swarm Optimization Algorithm) was improved. In the improved PSO algorithm, either the dynamic adjustment inertia weight of the algorithm or the introduction of mutation of the algorithm, the time consumed was both better than that by the standard PSO algorithm. The maximum result was obtained when the two algorithms were combined. The standard PSO algorithm and the improved PSO algorithm, all of which are on the basis of the dislocation theory, were adopted to deduce the three-dimensional slip rate of Qilianshan fault in the middle and eastern segments. Results showed that the time consumed by the improved PSO algorithm was reduced by36.34%by the standard PSO algorithm.4. The relative weight ratio relationship among the characteristics of the fault movement, horizontal displacement, elevation change, and gravity variation when the three kinds of data were jointly used to inverse the fault parameters. When the fault was mainly in the state of strike-slip, the weight of the data in the horizontal displacement was the maximum, the gravity data came next, and the minimum was the weight of the elevation change data. When the dip-slip was the major factor of the fault, the weight of the elevation change data was greater than that of the gravity change data. When the fault was mainly in rifting, the weight of the gravity change data was the maximum, that of the elevation data came next, and that of the horizontal displacement data was the minimum.5. A model was established in a fixed coordinate system between the crust horizontal movement and the gravity changes in the external earth. Taking into account the GPS in China’s western region, level, and some observation data as well as the local elevation data, the time and space variation characteristics of the gravity field were calculated, which were caused respectively by the crust horizontal movement and the vertical movement in the western area of China. The gravity change by the numerical simulation of the crustal horizontal movement was compared with that through the GRACE observation. Results showed that the magnitude of the two gravity changes was close, and the graphics contour was similar.6. The rate of the crustal horizontal movement and vertical crustal movement were investigated for the first time by the satellite gravity data in western China. Results showed that the characteristics of crustal horizontal movement in western China was clockwise from south to north with a trend of moving eastbound except Kunming in which the movement was from north to south. Along the south-north direction, the horizontal movement velocity was gradually declined. The south-north movement rate on the Qinghai-Tibet plateau was10～35mm/a, whereas the east-west movement rate was1～25mm/a. On the Tarim Basin, the south-north movement rate was5～15mm/a, whereas the south-north was4～7mm/a. The trend of the vertical crustal deformation in western China was up in south but down in north. In the southern Himalayas, the crust rose in a largest speed, reaching10mm/a. In the southern Junggar Basin, the vertical crustal movement rate was between-3～-5mm/a. The sedimentation rate northward trended to increase with the maximum rate of-9mm/a.