Instrumental seismicity catalog of Iran for moderate and strong earthquakes was provided by using the reports of the International Seismological Center (ISC), National Earthquake Information Center (NEIC), National Oceanic and Atmospheric Administration (NOAA), Moscow, Nowroozi and the others.
After analyzing this catalog we observed a series of heterogeneities concerning the homogeneity of magnitude determination throughout time.
As it is known, the earthquake catalog for shocks with mb>5.0  after 1964 (installation of the World-Wide Standardized Seismograph Network) is complete and the seismicity rates are typical of all decades in the century. Under this postulate for the period of 1920 to 1963 and due to the use of different formulations and criteria to calculate the parameter magnitude, we observed that the body wave magnitude of events with mb>6.0 was systematically overestimated by as much as 0.7 magnitude unit, relative to mb assigned to shocks occurring after 1963. After removing these heterogeneities, the new catalog was obtained. The revised catalog also includes scalar moment tensor (M0) for each event with magnitude M (M=mb  M<6.0, M=Ms  M>=6.0) where M0 is not provided in Harvard’s CMT catalog.