TECTONIC BACKGROUND AND SPATIAL CORRELATION FRACTAL DIMENSION OF STRONG EARTHQUAKES IN TAIWAN, CHINA

In recent years, many fractal studies have been made in aspects of time, space, and intensity of earthquakes, but most of them are limited to single fractal (capacity dimension D 1 and information dimension D 2). It is found that single fractal is not enough to characterize the temporal and spatial fractal properties of earthquakes and commonly has a very narrow linear non-scale range. Moreover, single fractal dimensions cannot be obtained in some cases. In this paper, therefore, the correlation fractal dimension is adopted to analyze spatial characteristics of seismicity in Taiwan area. By use of plentiful earthquake records from the last century in Taiwan area, the correlation fractal dimensions for each seismic region, zone, and segment in this area are calculated, and then the fractal characterization for hypocentral distribution of earthquakes can be quantified. Finally, the relationship between the spatial correlation dimensions and the seismogenic environments in this area is construed synthetically. The major results are as follows: 1) the correlation fractal dimensions of the eastern seismic region of Taiwan area differs from that of the western region, owing to the different tectonic settings of the two regions; 2) each seismic region can be subdivided into different seismic zones based on the difference of plate tectonics, crustal structure and the distribution of active faults. Each zone has its distinctive correlation fractal dimension; 3) the different segments of each seismic zone have different characteristics of earthquake clustering, and hence have different correlation fractal dimensions. The results of this study indicate that there exists a good correlation between the spatial images of seismic activity obtained from correlation fractal dimension analysis and the corresponding seismo-tectonic settings.