Spatial variation of earthquake hazard parameters in the Zagros fold and thrust belt, SW Iran

Abstract

In this paper, the parameters including maximum regional magnitude (M max), β-value, mean seismicity rate (λ) and mean recurrence time were calculated for the Zagros belt. The mapping of parameters shows that there are several seismogenic zones in the Zagros with different seismic activity patterns. The results of calculation of the parameters for each seismogenic regions show that the parameters such as β-value, mean activity rate, annual probability and mean return period of events have been decreased from NW Zagros to SE with exception of Qatar–Kazerun transverse fault zone. This pattern is consistent with the increasing convergent rate from 4.5 ± 2 mm/year in the northwestern to 9 ± 2 mm/year in the southeastern part of the Zagros range (Vernant et al. in Geophys J Int 157:381–398, 2004). The anomalous values of seismic parameters are observed for the two transverse lineaments of the Zagros, Qatar–Kazerun fault zone and Zagros–Makran transition zone. These zones are characterized by high seismicity rate, low β-value and mean return period of earthquakes. The highest value of M max coupled with very low seismic activity rate is observed for the MRF. It seems, in this zone, seismic energy is being released by a few relatively large earthquakes with longer return period. The other regions in the Zagros are characterized by high β-value, low seismicity rates and long recurrence time. The differences in the seismicity parameters are due to differing stress regimes and geological or structural heterogeneity of various parts of the Zagros belt .