Abstract
Mandelbrot introduced a fractal dimension to analyze complex geometrical sets. It is desirable to extend the fractal theory so as to be applicable to non-geometrical objects. For this purpose, one of the present authors intro-duced several fractal dimensions of a state for dynamical systems. These fractal dimensions provide new measures describing the complexity of the systems. In this paper, we apply a fractal dimension of a state to the analysis of earth-quake, and it is shown that the fractal dimension is useful to classify earth-quakes.
