r Tarinejad - Assistant professor, Faculty of Civil Engineering, University of Tabriz, Iran
Taghi Mahini - MSc. Student, Faculty of Civil Engineering, University of Tabriz, Iran
M. T. Ahmadi - Professor, Faculty of Civil Engineering, Tarbiat Modares University, Tehran, Iran

Effect of topographic amplification during earthquakes has been recognized as an important factor on ground motion. There are a lot of studies by numerical methods such as finite element and boundary element methods. However, the numbers of experimental investigations of topographic effects are limited. During ambient vibration tests on Shafaroud dam site, 24 Oct 2007 Caspian Sea earthquake with 3.2 Magnitude happened and recorded by the three installed seismometers (in the base and wall of the canyon) along the free field of the Shafaroud dam axis. These earthquake records are used in order to evaluate the topographic amplification effects in this site. Classical signal processing method is used in order to obtain different spectra. Amplification factors are obtained using classical spectral ratio method using one reference point (station located on the base of the canyon) and Nakamura technique. In order to show the efficiency and accuracy of Nakamura method for obtaining topographic amplification factors, the results of these two methods are compared with each other.

Topographic Amplification, 24 Oct 2007 Earthquake, Shafaroud Dam site,Nakamura, Spectral Ratio