H Rahnema - Assistant Professor, Department of Civil and Environmental Engineering, Shiraz University of Technology, Shiraz, Iran
M.H Bozorgi - Ms Candidate of Earthquake Engineering, Department of Civil and Environmental Engineering, Shiraz University of Technology, Shiraz, Iran

The spectral ratio between horizontal and vertical components noise (H/V ratio) of microtremors hasbeen used to estimate fundamental resonance frequency of the site. In this study we investigate theapplication of the wavelet analysis to improve the (HVNR) technique for site effect estimation. Waveletanalysis has been widely used in the last decade for its capacity to localise the signal in both the time andfrequency domains. This property, which derived directly from multiresolution analysis provide us theability to decompose a signal in a well localized set of coefficients and identify the non-stationaryportions of it.In the present study we use the WT in order to eliminate the non-stationarities inmicrotremor signals before we calculate the spectrum of each one using conventional FFT algorithms.

HVNR, Wavelet transform, non-stationary, FFT algorithm