Fractal Characterization Of Seismic Activity In The Taiwan Area

By the analysis of plate tectonics, the distribution of active faults, and crustal deformation, the Taiwan area is divided into two seismic regions: the east one and the west one on the base of the difference of seismic activity characterization and plate tectonic movement. Then according to neotectonic and current tectonic movement, tectonic stress field, and seismotectonic movement, the east region can be devided into 3 seismic zones: the Ryukyu Arc-Trench Seismic Zone, the Longitudinal Valley Seismic Zone, the Luzon Arc-Trench Seismic Zone, and the west region also can be devided into 3 seismic zones: the Hsinchu Fault Depression Seismic Zone, the Peikang Lifted Seismic Zone, and the Taiwan Southwest Basin Seismic Zone.With the analysis of tectonic environment and seismicity, correlation fractal dimensions of each region, each zone, and each sect are calculated and the following results were obtained: 1. The spatial distribution of earthquakes has fractal characteristics. Different correlation fractal dimensions of earthquakes reflect different tectonic environments where earthquakes can occur. 2. The correlation fractal dimensions between the east region and the west one have a rather distinct difference. The dimension of the east region is bigger than the west region, for the earthquakes of the east region and the west region have different properties( earthquakes of the east are interplate ones, and earthquakes of the west ones are intraplate ones). The distribution of interplate earthquakes is rather even, its average dimension (M>=5.0) is 1.473, while the distribution of intraplate earthquakes is rather inhomogeneous, its average dimension (M>=5.0) is 1.370.Using the earthquake catalog of Taiwan area in 11 years, we calculated the multifractal dimensions Dq and f ( a ) is caculated, then Dq-q curve, multiscale fractal chart f ( a ) - a , and Dq -t curve are plotted. After integrated analysis , the following conclusions are drawn:1. The temporal structure of earthquakes is not single fractal but multifractal, so the research should be done by multifractal means in order to reveal the potential rule.2. Within 1 to 2 years before and after an major of Taiwan, most Dq-q curve and f ( a ) - a chart in the zone where the earthquakeoccurred appeared an abnormal shape. In other word, Dq of +q went down and Dq of -q went up while the span of f ( a ) - a chart was widened and peak moved to right before earthquake.