Study On The Relationship Between Fractal Characteristics And Seismicity Of Space - Temporal Distribution In Yunnan Province

Fractal theory is an important branch of nonlinear science, which studes the ubiquitous geometric objects that are of complicated, irregular and non-differentiable shapes in nature. Previous studies have indicated that the occurrence of earthquake is a complicated nonlinear process, and its spatiotemporal distribution is of complex fractal characteristics. The seismic parameters have some relationship to regional seismic spatiotemporal fractal characteristics.Yunnan locates in the east margin of the collision zone between the Indian Plate and the Eurasian Plate in the Chinese continent, where the crustal movement is violent, seismicity is high and earthquake disasters are frequent.Based on the theory of nonlinear science, and the latest research results of domestic and international seismic fractal, firstly, the fractal calculation mathematical models of seismic time series, focal points and the main fractures of the seismic zones in Yunnan have been given in this study; Then with the aid of GIS spatial analysis tools, the fractal dimension and the space distribution fractal characteristics of the focal points and the main fractures within the whole province and the major seismic zones have been calculated and analysed respectively. At the same time, the rescaled range analysis (R/S) method has been applied to calculate the Hearst exponent of seismic time sequence of each seismic zone, and the seismic time series variation trend and self affine fractal characteristics of the zones have been reviewed. Secondly, multi variable regression analysis has been adopted to analyse the correlation between seismic fractal, seismicity parameters b and seismic activity factors (the fractal characteristics of seismic frequency time series H, the maximum expected magnitude parameters alb, the annual earthquake occurrence rate v, the strain energy release rate (?) and the upper limit magnitude Mu). The main influence factors and principal components that impact the seismic activity of each seismic zone, and the relationship between seismic parameters and seismic fractal characteristics of each seismic zone have been summarized. According to the seismic parameters Da, H,b, v, Mu, a/b,(?), the potential seismic risk level of each earthquake zone of Yunnan Province have been given to provide a new scientific basis for earthquake prevention and disaster reduction and emergency response of Yunnan Province in the future.The following conculusions have been obtained from the study:1. The value of fractal dimension of focal points of Yunnan and the main seismic zones varies from0.3to0.5, with the smallest value0.3286for Xiaojiang seismic zone, and the largest value0.483for Lancang-Gengma seismic zone. The fractal dimension value of main fracture varies from0.97to1.2, with the smallest value0.975for Mabian-Daguan seismic zone, and value greater than1.0for the rest seismic zones, compared to others Zhongdian-Dali seismic zone is of the largest value1.199. The fractal dimension of focal point is0.4047, and the main fault fractal value is1.1661for Yunnan Province as a whole study area.2. The seismic frequency of the time series of Yunnan province and the major seismic zone are of self affine fractal characteristics. The descending order of the Hearst exponent values for the seismic zones is0.8729(Yunnan),0.8128(Tengchong Longling),0.7763(Shimao-Puer),0.6645(Tonghai-Shiping),0.6512(Mabian-Daguan),0.6039(Lancang-Gengma),0.5202(Zhongdian-Dal),0.4582(Xiaojiang). The values of H of Yunnan province and Tengchong-Longling are both close to1.0, which indicates that the seismic frequency of the tow zones has a long lasting variation process. It means that the future seismic behavior of the zones may be influenced by the past situation and the future trend of seismic frequency will be more consistent with the past on the whole. The H values of Xiaojiang and Zhongdian-Dali are close to0.5, which means that the varying process of seismic frequency distributions with time for the tow zones is nearly randomly independent. The H value of frequency time serie of magnitude greater than4.5of Yunnan is obviously larger than that of other of China and its adjacent areas (Which is0.721). It means that the frequency of moderate-strong earthquakes’ occurrence of Yunnan may has stronger regularity and more durable than other parts of China and its adjacent areas, which reflects that Yunnan is a earthquake prone area;3. The simple regression analysis method has been used to analyze the the relationship between the fractal dimension value of focal points and the fractal dimension value of main fractures. The result shows that there is no obvious linear relationship between them;4. When taking bas the dependent variable, v, Mu, a/b,(?), H as independent variables in multiple regression analysis, it has been found that there is a significant linear correlation between b and Mu,a/b,(?). When taking the fractal dimension Df as the dependent variable, b, Mu,(?), v,alb, H as independent variables in multiple regression analysis, it has been found that there is a significant linear correlation between Df and b, Mu, v, alb, and these is a positive collelation between b,(?), alb and Df, a negative correlation between v and Df, and the effect of Mu, H on Df is smaller. When taking Da as the dependent variable, b,Mu,(?),v,a/b as independent variables in multiple regression analysis, it has been found that there is a significant positive correlation between Da and b, and Mu,(?),v,a/b have no significant influence on Da.5. By the results of previous studies and studies done here in this articale, it can be concluded that Yunnan may have entered into the first period of earthquake activity in21st century since2014, and the stronger earthquake prone area may be in the eastern part of Yunnan Province. According to the calculated seismic activity factors Da, H, b, v, a/b,(?), combined with the historical seismic background and major earthquake recurrence period of Yunnan, it can be initially identified that the seismic zones, such as Tengchong-Longlin, Lancang-Gengma, Daguan-Mabian may of relatively higher seismic risk level over a period of time in the future than other seismic zones.