Regional variations and correlations of Gutenberg-Richter parameters and fractal dimension for the different seismogenic zones in Western Anatolia

We investigated the regional variations of Gutenberg-Richter (G-R) parameters (a and b) and fractal (correlation) dimension (D-C) and relations among these parameters for the different regions in Western Anatolia (WA). The whole examined area (26-33 degrees E, 33-40.5 degrees N) is divided into 15 different seismogenic regions based on their tectonic and seismotectonic regimes. We used database including 69,182 earthquakes for the instrumental period from 1900 to 2011. We calculated b value, which is the slope of the frequency-magnitude Gutenberg-Richter relationship, from maximum likelihood method (ML) and D-C value, which is the slope of log(10)C(r) versus log(10)r, from correlation integral using the least-squares (LS) method. Computed values for 15 different seismogenic regions are mapped using different color scale for different range of values of b and D-C. Regional distributions of these parameters reveal information about regional variation of stress level and geological complexity. We concluded Aegean arc and Aegean islands, Aliaga fault and Buyuk Menderes Graben the most vulnerable regions for occurrence of the large earthquakes in WA considering the computed lowest b-values and the highest D-C-values in these regions. Since D-C/b values are the highest in these regions, this ratio may be used as an indicator of earthquake hazard levels of different seismogenic zones in a studied region. An effort is made to find relationships between the G-R parameters and fractal dimension. We observed negative correlation between D-C and b values and positive correlation between D-C and a/b values for different regions of WA. We observed that the relationship between a/b and D-C can be used for seismicity, earthquake risk and hazard studies because of the computed high correlation coefficient and fewer scattering of these parameters. (C) 2012 Elsevier Ltd. All rights reserved.