Gerardo Colangelo

Monofractal and multifractal characterization of geoelectrical signals measured in southern Italy

Abstract Fractal tools have been used to characterize the temporal fluctuations in the dynamics of hourly geoelectrical signals, measured from January 2001 to February 2002 by four stations installed in Basilicata region (southern Italy). Three stations (Giuliano, Marsico and Tito) are located in a seismic area, and one (Laterza) in an aseismic area. Monofractal approaches (Lomb Periodogram, Higuchi method and detrended fluctuation analysis) have been used to identify in a wide range of timescales scaling behaviour, that indicates the presence of correlated temporal fluctuations and long-range dependence. The multifractal formalism leads to the identification of a set of parameters, derived from the shape of the multifractal spectrum (the maximum α0, the asymmetry B and the width W) and measuring the “complexity” of the signals. Furthermore, the multifractal parameters have revealed to well discriminate geoelectrical signals measured in seismic areas from those recorded in aseismic areas.

QUANTITATIVE DYNAMICS IN GEOPHYSICAL PARAMETERS SIMULTANEOUSLY RECORDED IN THE SOOS NATURE PARK (CZECH REPUBLIC)

Time dynamics of self-potential, geochemical and meteorological parameters, simultaneously recorded in a CO2 degassing area at Soos, NW-Bohemia (Czech Republic), have been investigated. The power spectra, behaving as power-law function of the frequency, show the presence of colored-noise-type dynamics. The Higuchi analysis reveals the observed geophysical signals to have the property of fractal curves, with the identification of different scaling regimes. The Detrended Fluctuation Analysis, removing trends and non-stationarities, has shown that the signals present clear fingerprints of long-range correlated fluctuations.

ANALYSIS OF CORRELATION PROPERTIES IN GEOELECTRICAL DATA

This paper considers four geoelectrical time series, measured in a seismic area of Southern Italy. Lomb Periodogram method, Higuchi analysis, Detrended Fluctuation Analysis (DFA) and the mean distance spanned within time L are used to discuss the correlation properties of these signals. The values of the scaling exponents from these methods of the geoelectrical data indicate that the long-range correlations are present. Furthermore, it is found that these correlations are all linear.