Firouzabad-Kojour (Baladeh) Earthquake of 28 May 2004, Mw=6.3
A moderate earthquake (Ms=6.3) struck the coastal region of north of Iran and the central Alborz on 28 May, 2004 was responsible of several damages and about 35 casualties. The mainshock was followed by a large number of aftershocks, the largest one reaching Ml=4.8, based on the analysis of local waveforms. The coordinates of the mainshock was determined as 36.3N for latitude and 51.6E for longitude. The analysis of aftershocks indicates that the seismic activity migrate from east where the mainshock occurred toward west close to the location of the largest aftershock (36.36N, 51.45E). The aftershocks distribution had 30 km long and trends NW-SE parallel to the North Alborz and Khazar faults. The focal depths comprised between 10 and 28 km, unusually deep for Iran. Distribution of aftershocks cluster on cross-section defines a fault plane which dips at 40-50 degree south-westward. Its upward continuation can be related to either North Alborz or Khazar faults. Most of the focal mechanisms are consistent with reverse faulting on NW-SE trending faults, parallel to the main active structures of the region.
Reference: Mohammad Tatar and Amir Mansour Farahbod, (2007), the 2004 may 28 Firoozabad-Kojour (Iran) earthquake, ms 6.3, and its aftershocks based on recorded data at local seismological stations.