All reported earthquakes of magnitude 4 and above which occurred between 20 and 40 1\orth Latitude and between 40 and 75 1 East Longitude during the 20 years period ended on June 30,1977 are analysed. On the basis of computed strain release, the counter maps of seismicity are constructed for each 5-years period as well as for the 20-years period. The maps are,then,compared in the view to study the temporal and spacial variations of seismic activity in different seismic zones of the area. Statistical analysis of the data are carried out,independently,for three seismic zones along Zagros and Alburs ranges and in eastern part of Iranian plateau in order to assess a and b values for each 5years period as well as for the 20-years period.

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