Fractal approaches in investigating the time dynamics of self-potential hourly variability

Fractal tools have been used to investigate the time dynamics of hourly self-potential data, recorded during the year 2001 by five geoelectrical stations located in one of the most seismic areas of southern Italy. Scaling behaviour has been revealed by means of different statistics: the Lomb Periodogram method, the Detrended Fluctuation Analysis, the Higuchi analysis and the mean distance spanned within the time L. The values of the scaling exponents estimated by means of these methods indicate that the temporal. fluctuations of the geoelectrical signals are not typical of purely random stochastic processes ( i. e. white noise), but evidence the presence of long-range correlations. Furthermore, it is found that these correlations are linear.