Investigating the time-correlation properties in self-potential signals recorded in a seismic area of Irpinia, southern Italy

Recent studies have shown that many natural phenomena are characterized by temporal fluctuations with long-range power-law correlations, suggesting a fractal geometry of the underlying dynamical system. The presence of power-law correlations are detected in four time series of self-potential signals, measured in a seismic area of southern Italy, by means of the Detrended Fluctuation Analysis (DFA), a method that permits the detection of long-range correlations in nonstationary time series. Results show scaling behaviour for all the signals recorded, indicating the presence of fractal features expressing a long-term correlation quantified by the numerical value of the scaling exponents. Our findings suggest a possible correlation between the earthquakes occurred in the area investigated and the relative maxima/minima of the mean and the standard deviation of the scaling exponents. Furthermore, the normalized average and standard deviation curves for all the signals tend to converge in correspondence with an earthquake.