Long-Term Seismicity Behavior of the Zagros Region in Iran

Abstract

To achieve a comprehensive attitude about seismicity, it is necessary to consider spatial and magnitude distributions of earthquakes. Earthquake distributions in space and magnitude can be quantified by means of spatial fractal dimension D(s) and Gutenberg–Richter b value. In this paper, b value and D(s) are used to evaluate seismicity of the Zagros zone (Iran) in time interval 1964 to 2012. Seismic catalog of the Zagros zone is extracted from unified seismic catalog of the Iranian Plateau. The b value and D(s) are estimated using frequency–magnitude distribution, Kijko-Sellevoll (Bull Seism Soc Am 79(3):645–654, 1989) and correlation integral methods. Correlations between spatial variations in b value and D(s) along individual profiles across the North Zagros and the Central Zagros indicate different stress release regimes for North and Central parts of the Zagros zone. Evaluation of b value with respect to depth along the profiles indicates larger b values at shallower depths. Temporal variations in b value and D(s) are also obtained from background seismicity to evaluate seismicity behavior of the Zagros zone. Our results indicate high b values and moderate D(s) for seismicity of the North Zagros, while seismicity of the Central Zagros has low b values and high D(s) during time interval 1964–2012. Asperities of the Main Zagros Thrust are also located by investigating ratio D(s)/b along the Main Zagros Thrust.