Earthquake ground-motion prediction in the Khalkhal region, NW Iran

Understanding seismic sources in a region help us to identify the level of ground motion. The area around Khalkhal city in the south of Ardabil province, northwest Iran, is a seismic region that is specially, complex from a geodynamic and tectonic point of view. Prevailing tectonic regimes in different geologic time intervals have caused at least two deformation episodes recorded by faults, folds and other tectonic structures. These structures indicate that the dominant tectonic regimes have been compressive. Examination of the seismic power of currently active faults and software analysis of their focal mechanisms, show that major activity in the region is due to faults with trend north-south and northeast-southwest. The results of this study indicate the seismic capacity of the region and the likely occurrence of earthquakes with a magnitude greater than two on the Richter scale. Also, they show that the probability of earthquakes with magnitudes above 5.3 on the Richter scale is one in one hundred years. High a- and b-values indicate the frequency of earthquakes with low magnitude and the generally high seismicity in the region.