S.M Haeri - Civil Engineering Department, Sharif University of Technology. Tehran, Iran
M Hajialilue Bonab - Iran Marine Industrial Co . (SABRA), Tehran, Iran

One of the methods by which one can state dynamic characteristics of soil of an area. is the measurement and study of microtremors. Microtremors have been measured on ۱۴۳ sites located in the city of Tabriz, Iran. These sites were chosen on profiles that covered the city in two orthogonal directions. Three components of the microtremors were measured on sediments and associated rock sites. Spectral amplification with respect to rock has been implemented in addition to Nakamura method [۶] for Fis ۱Vy to interpret the results of measurements for calculation of the natural period of the ground due to horizontal dynamic loadings Due to the importance of the vertical component of earthquakes (as been observed in the recent earthquakes, e.g. Kobe ۱۹۹۵), the vertical component of the rnicrotremors has been studied in this research as. well. On such basis a method was proposed to study the natural period of deposits for vertical ground vibrations