| Earthquake is one of the most serious geological disasters on the planet which created a great loss to human society. It causes serious casualties and economic losses. China is one of countries who suffer geological disaster the most serious, while Sichuan&Chongqing located in southwest of China is more concentrated and more earthquake-prone area. With the development of social economy and acceleration of urbanization, earthquake has become a tremendous resistance to economic development in Sichuan&Chongqing. Therefore, enhancing study in earthquake is a necessary condition for taking precautions against and even reduce disaster and realize the sustainable development of society. Fractal theory providing a new idea and methods to study earthquake disaster since being born.Earlier fractal researches of earthquake are mainly focused on it’s basic conceptions, methods, relations, and discussions of temporal and spatial characteristics before and after earthquakes. Area studied earlier is mainly confined to an earthquake in a small area or entire Chinese earthquake partition, while there are few fractal studies in the view of meso geographical phenomena on spatial scale. Earthquake fractal study based on tectonic units not only be beneficial to trial study of regional seismic fractal, but also to reveal fractal characteristics of earthquakes, to promote study earthquake occurrence mechanism and extend width and depth of earthquake fractal research.Based ont the fractal theory and research methods applied in current seismic studies, this paper took "Sichuan Earthquake Record", "Sichuan Tectonic Unit Map" and "Sichuan Province Geological Map" as basic data, taking Geographic Information System (GIS) as technical support platform, adopting grid method, capacity dimension, information dimension and G.R etc. as formulas to calculate dimension value of earthquake space, time and energy for each tectonic unit in Sichuan&Chongqing. And using these formula to calculate fault dimension value for each tectonic unit in Sichuan&Chongqing. Then reveal earthquake seismic fractal mechanism from the different research perspective. The main contents and conclusions of this paper include:(1 Systematically discussed spatial fractal characteristics of tectonic unit in Sichuan&Chongqing area. Seismic spatial distributions of tectonic units within a certain space scale have significant fractal characteristics. Seismic spatial distributions of fractal dimension values of secondary tectonic units is clearer than that of first tectonic units. Seismic spatial distribution fractal dimension value is negatively correlated with average distance between most two adjacent earthquake points. There is no corresponding relationship between seismic spatial distribution fractal dimension value and times of earthquake happened in tectonic unit while it shows a positive correlation between seismic spatial distribution fractal dimension value and spatial distribution density. Generally speaking, seismic spatial distribution fractal dimension value interrelated with complexity of tectonic units and strength&weakness of crustal movement. Its information dimension is quantitative indicator for strength and weakness of tectonic units activities.(2)Systematically discussed the temporal fractal characteristic of tectonic unit and of time series before and after the earthquake as well in Sichuan&Chongqing area.. Seismic time distribution structure of tectonic units within a certain time scale have significant fractal characteristics. Seismic time fractal dimension value reflects in-homogeneity of time of earthquake happened. There are some corresponding relationship between seismic time distribution fractal dimension value and time of earthquake happened. The greater the proportion earthquake point occupied(Surfece wave magnitude> 5) is, the smaller the information dimension value of time distribution of earthquake point becomes. Seismic time series fractal characteristics of Sichuan-Chongqing region existed within a certain range of time scales objectively. Fluctuations in seismic time series fractal dimension can reflect the strength of seismic activity. Before the earthquake, dimensional seismic time sequence information may appear abnormal rise, abnormal decline and transition variation.(3)Systematically discuss energetic fractal characteristics of tectonic unit in Sichuan&Chongqing area. Seismic energy distributed structure of tectonic units has a scale in-variance fractal characteristic. Energetic fractal dimension values can quantitatively reflect the strength and weakness of the regional tectonic movement. Seismic energetic distributed fractal dimension value is negatively correlated with ratio of earthquake quantity (Surface wave magnitude≥6) to earthquake quantity (4≤Surface wave magnitude<6). The smaller the proportion of big earthquake happened in tectonic units is, the greater energy fractal dimension value of earthquake point becomes.(4)Systematically discussed the fractal characteristic of fault lines of tectonic units, and the relationships between earthquakes and fault lines in Sichuan&Chongqing area.Fault spatial distributed structure of tectonic units has significant fractal characteristics within a certain time scale. The fractal analysis indicates that a more complex spatial distributed structure of fault and stronger tectonic activity and a better development tectonics followed a bigger fault capacity fractal dimension.There is no corresponding relationship between fractal dimension value of fault spatial distribution and quantity of fault in first-level tectonic units, while it is significantly correlated with quantity of fault when this number is under 0.05 in the secondary tectonic units. Certain corresponding relationship exists in spatial distribution between earthquake point and fault. Earthquake points mainly distribute around deep fault zone. Moreover, there is a certain corresponding relationship seismic spatial fractal dimension and fault fractal dimension. A higher seismic spatial fractal dimension value follows a higher fault fractal dimension value. |
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