Historical data suggests the occurrence of a major earthquake every 2-3 years in the country. In the 20^th century alone, 20 major earthquakes claimed more than 140,000 lives, destroyed several villages and cities and caused extensive economic damage to Iran. Prior to the recent Bam earthquake, more than 200 people were killed in the Qazvin earthquake (June 2002), more than 2500 people died in an earthquake in eastern Iran and North-western Iran (1997), and about 40,000 persons lost their lives in Iran’s worst recorded earthquake affecting the Caspian areas of Gilan and Zanjan in 1990.

Source: UN Flash Appeal, Bam Earthquake of 26 December 2003. Islamic Republic of Iran Relief, Recovery and Immediate Rehabilitation. Available at: http://www.emro.who.int/eha/UN-Flash-Appeal

Another useful link: http://neic.usgs.gov/neis/world/iran/sig_eq.html