Study On Deformation Characteristics And Seismic Risk Of Fault Zone In The Middle And Middle Region Of The Middle And Eastern China Province Based On Gps Data

Yunnan is located in the southern section of north-south fault zone in China.Because of the tectonic complexity and large earthquakes once happened in this region, this region is one of the most frequent seismic activity in China region。By studying the block movement characters, the fault locking characters and seismic hazard, we can draw a better conclusion about the tectonic stress field, geodynamic mechanism, seismic hazard and risk assessment in the mid Yunnan and its surrounding areas.In this study,we divided the study area entirety based on the previous research results.The active deformation and kinematic of the study area can be explained by a block model using GPS vectors.Secondly, we used DEFNODE program to construct a 3D elastic dislocation model. GPS vectors, block model and dislocation model were used to invert slip rate, slip-deficit rate and Euler pole. Last but not least, we collected focal mechanism solutions and the historical seismicity, using regressions and taking into account the results of our studies,we predict the magnitude of the next credible big earthquake along the different faults in the study area.The main conclusions are as follows:1.Blocks in our study are consistent with the clockwise rotation relative to stable Eurasia. Both Huanan block and Miandian block’s Euler rotation vectors refer small and stable relative to stable Eurasia. Daliangshan block’s calculation results is larger than the other blocks, and the movement posture is different from its surrounding blocks. The other calculation results truly reflect the movement characteristics.2.Daliangshan fault, the middle segment of the Red River fault, Longling-Lancang fault, Lijiang-Xiaojinhe fault and the middle-northern segment of the Nantinghe fault are completely locked, but other faults are weakly locked. In the inversion, the Anninghe, Zemuhe, northern segment of Daliangshan, southern segment of Daliangshan, Xiaojiang, northern segment of Lijiang-Xiaojinhe, southern segment of Lijiang-Xiaojinhe, Chenghai, Nantinghe and Litang faults, with their left slip rates being 5.7 ± 0.2, 4.7 ± 0.4,5.8 ± 0.3,4.9 ± 0.2,10.7 ± 0.2,0.1 ± 0.1,4.5 ±0.2,5.1±0.1,7.5±0.4,5.2±0.2 mm/yr, respectively. The Nujiang-Longling-Lancang, northern segment of Red River, middle-northern segment of Red River and middle segment of Red River faults, with their right ship rates being 5.0±0.2,1.9±0.2,0.2±0.5,1.8±0.4 mm/yr. We calculated the Euler pole relative to Huanan block is respectively :Dianzhong block(95.7708°,25.8285°,-0.8370°/Ma); Xianggelila block(94.8354°,26.6607°,-1.2457°/Ma); Baoshan block(94.0704°,28.4092°,-0.9526°/Ma); Daliangshan block(100.8041°,26.7292°,-1.4512°/Ma); Jinggu block(95.7114°,26.2380°,-0.5546°/Ma); Miandian block(96.4726°,31.5007°,-0.4654°/Ma); Yajiang block(98.1289°,27.4841°,-1.5316°/Ma)。3.We concluded that since January, 1976, the earthquake calm area gradually decrease over 40 years, and finally formed the Mianning-Xichang segment of Anninghe fault, northern segment of Lijiang-Xiaojinhe,southern segment of Litang fault,Nanjian-Gengma segment of Nantinghe fault,northern segment of Red River fault, middle segment of Red River fault,northern segment of Red River fault are seismic gaps. We used the regression to predict the potential magnitude of Anninghe, Zemuhe, Daliangshan, Xiaojiang, Red River, Lijiang-Xiaojinhe, Chenghai, Nujiang, Nantinghe, Longling-Lancang and Litang faults are represently 7.1,7.4,7.1,7.3,7.3,6.7,7.0,6.9,6.9,6.8,6.9.