Megacity of Tehran with a population of more than 8 million is located in a very active region, both in terms of tectonic and seismicity. Due to socio-economic and political importance of Tehran, in 1994 IIEES has initiated a comprehensive geotechnical hazard study in Tehran. The geotechnical microzonation part of the program was composed of two parts: site effect and liquefaction potential microzonation. Site effect microzonation was started for south of Tehran using one dimensional site response analysis and microtremor measurement. The results of these studies were compiled and presented in three microzonation maps for south of Tehran including: natural site period map, dynamic site period map and the PGA distribution map. Based on the preliminary result, comprehensive studies for south as well as for north of Tehran have been started. Liquefaction potential study of Tehran alluvium was started in 1995. Considering that the northern part of the Tehran is located on coarse grain clayey alluvium and deep water table the liquefaction study was concentrated in the south of Tehran. The liquefaction potential was evaluated and the microzonation maps were developed. A more detailed investigation is now underway to assess more accurately the liquefaction potential for the south of Tehran
