Fractal Analysis as a Tool to Detect Seismic Cycle Phases
This chapter concerns the study of the temporal evolution of seismicity in a particular region, through a time repeated fractal analysis of the spatial distribution of the seismic events. The technique is applied to the NE—Italy Friuli seismic region, where a local seismic network has been active since 1977 (OGS 1977–1981, 1982–1990). Fractal dimensions have been calculated at fixed time intervals of thirty days. The spectrum of the time series thus obtained reveals that in this region the seismicity is characterized by a sort of periodicity, with periods that vary from one year to about four years, superimposed onto a longer period term.
The comparison of these results with the geodetic measurements in the same region suggests a ‘periodic’ variation of the stress field as the cause of both phenomena, and confirms the usefulness of this kind of fractal analysis in the study of the seismic process.
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