Fractal methods in self-potential signals measured in seismic Areas

Abstract

Summary: The self-potential (SP) signals are mainly generated by the streaming potential, which causes a voltage difference when a fluid flows in a porous rock. In seismic focal areas, this effect is strengthened by the increasing accumulation strain, which can produce dilatancy of rocks. Therefore, tectonic processes can be directly revealed by the investigation of the temporal fluctuations of SP signals, which may be useful to monitor and understand complex phenomena related with earthquakes. Can the concept of fractal be used to qualitatively and quantitatively characterize an SP signal? Fractals are featured by power-law statistics, and, if applied to time series, can be a powerful tool to investigate their temporal fluctuations, in terms of correlations structures and memory phenomena. In the present review we describe monofractal and multifractal methods applied to SP signals measured in seismic areas. Persistent scaling behaviour characterizes SP signals, which, therefore, are not realizations of a white noise process. Furthermore, in multifractal domain SP signals measured in intense-seismicity areas and those recorded in low-seismicity areas are discriminated. © 2005 Springer-Verlag Berlin Heidelberg.