Multifractal analysis of Earthquakes in Central Alborz, Iran; A phenomenological self-organized critical Model

TL;DR

This study models earthquake activity in Central Alborz, Iran, using a self-organized critical model and multifractal analysis, revealing universal anti-correlated behaviors and links between activity and earthquake size.

Contribution

It introduces a phenomenological sandpile-like model incorporating regional observational data and analyzes multifractal properties under different external stimuli schemes.

Findings

Hurst exponent is below 0.5 in all cases, indicating anti-correlation.

More active stimulation sites lead to lower Hurst exponents.

The model links activity fields to geological features and earthquake probability zones.

Abstract

This paper is devoted to a phenomenological study of the earthquakes in central Alborz, Iran. Using three observational quantities, namely weight function, quality factor, and velocity model in this region, we develop a phenomenological dissipative sandpile-like model which captures the main features of the system, especially the average activity field over the region of study. The model is based on external stimuli, the location of which are chosen (\textbf{I}) randomly, (\textbf{II}) on the faults, (\textbf{III}) on the highly active points in the region. We analyze all these cases and show some universal behaviors of the system depending slightly on the method of external stimuli. The multi-fractal analysis is exploited to extract the spectrum of the Hurst exponent of time series obtained by each of these schemes. Although the average Hurst exponent depends on the method of stimuli (the three cases mentioned above), we numerically show that in all cases it is lower than $0.5$, reflecting the anti-correlated nature of the system. The lowest average Hurst exponent is for the case (\textbf{III}), in such a way that the more active the stimulated sites are the lower the value for the average Hurst exponent is obtained, i.e. the larger earthquakes are more anticorrelated. However, the different activity fields in this study provide the depth of the basement, the depth variation (topography) of the basement, and an area that can be the location of the future probability event.