Multifractal analysis of the spatial distribution of earthquake epicenters in the Zagros and Alborz-Kopeh Dagh regions of Iran

This paper shows how multifractal analysis can be used to characterize the spatial distribution of epicenters in the Zagros and Alborz-Kopeh Dagh regions of Iran. The main multifractal characteristics, Dq, f(?q), ?q, ?q and a set of multifractal parameters defined from the shape of the f(?q)-spectrum including the width of f(?q)-spectrum, nonuniformity factor, combined parameter, coefficients of steepness and asymmetry, and vertex of the ?(q)-spectrum have been determined. The results show that, in comparison with the Alborz-Kopeh Dagh region the epicentral distribution in the Zagros has a weak multifractal (i.e. less heterogeneous) structure. Although the f(?q) spectra of both regions were skewed, the directions of skewing were different. The two distinct multifractal distribution patterns in these regions reflect different underlying seismotectonic processes related to earthquake activity. The diffused seismicity with fewer larger earthquakes relative to smaller ones in the Zagros and relatively low level of discontinuous seismicity with sporadic occurrence of strong destructive events in the Alborz-Kopeh Dagh confirm our findings. The results further suggest that multifractal analysis provides us with a deep insight into the complex nature of distribution and geometry associated with earthquake-related phenomena that could not be discovered by any other means.