Regional variations and earthquake frequency–magnitude distribution and fractal dimension in the North of Central-East Iran Blocks (NCEIB)

Abstract

The Gutenberg–Richter parameters (a and b), fractal dimension (D C ), and relationships between these parameters are calculated for different regions of the North of Central-East Iran Blocks (NCEIB). The whole examined area (between 34°–36° N and 55°–61° E) is divided into 55 equal square grids. Both the a and b values for the frequency–magnitude distribution (FMD) and D C are investigated simultaneously from 55 equal square grids. By using the completeness earthquake dataset for earthquakes of the instrumental period from 1976 to 2015, it is concluded that calculated values of a, b, and D C imply variations of seismotectonic stress. The most vulnerable regions for occurrence of the large earthquakes in the NCEIB are considering the computed lowest b values and the highest D C values. The relationships among D C –b and D C –(a/b) are used to classify the level of earthquake hazards for individual seismic source zones, in which the calibration curves illustrate a positive correlation among the D C and b values (Dc = 0.609 b − 0.008) and also a positive correlation among the D C and a/b ratios (Dc = 0.069 a/b + 0.215) having similar regression coefficients (R2 = 0.80 to 0.87) for both regressions. It is observed that the relationship among a/b and D C may be used for evaluation of seismicity and earthquake hazard assessment because of the high value for correlation coefficients and limited scattering of the calculated parameters.