Fractal Analysis of Seismicity: Before and After the Chi-Chi Earthquake

It is generally believed that an earthquake occurs on an intricate network of faults which have similar shapes on all scales. This property is a kind of scale invariance which results in a power law distribution of scales where the exponential coefficient is a constant. This constant is related to the topographic dimension and is also referred to as the fractal dimension. This dimension is then used as a quantity to describe scale-invariant phenomena. In this study, the fractal dimension represents the fractal clustering of seismicity in a fracture system. The larger the fractal dimension is, the higher is the fractal density distribution of seismicity. In addition, an experiment on fractures shows a gradual decrease in the fractal dimension after fracturing with the passing of time. This strongly implies that a decrease in the fractal dimension over time may well lead to a large earthquake. To carefully monitor a change in the fractal dimension in a fracture system is, therefore, critical with regard to earthquake prediction. By studying the temporal and spatial distribution of earthquakes before and after the Chi-Chi earthquake. The present results, indeed, confirm the proposed theory.