Fractal ULF signatures related to seismic processes

Abstract

In order to detect seismo-related patterns that manifest themselves in fractal properties of ULF magnetic field variations, the fractal and multifractal analyses of the ULF data obtained from several stations were performed. As a result, two different behaviors of fractal parameters of the ULF magnetic field variations were detected. The first one has the certain co-seismic character and manifests itself in significant increase in fractal dimension synchronous with the rise of seismic activity. Another pattern can be interpreted as a manifestation of the seismic preparation processes, which is characterized by the significant gradual decrease in fractal dimension during the extended time period of several months. Also a new procedure of the local geomagnetic activity (LGA) level estimation was proposed. A correlation between the geomagnetic activity and the fractal dimension, and, consequently, the necessity of taking into a consideration the LGA level was demonstrated.