1566-1577Shear wave velocity (Vs) plays a fundamental role in soil dynamic problems and seismic analyses to estimate the site effect for earthquake geotechnical microzonation. During an earthquake the ground motion is significantly affected by the soil type, stiffness and geological condition. The shear wave velocity and Shear modulus are the applied variables in nonlinear site response analysis. As a part of microzonation study for the Babol city a total of 35 boreholes have been drilled in 35 km2 of the research area. The depths of these boreholes ranged about 25 to 30 m. SPT blow counts were taken in each 2 m depth. Many geophysical surveys, and generally 35 downhole logging surveys, are carried out in 35 mentioned boreholes for generation and measurement of shear waves in situ. According to the results of various in-situ tests, the variation of shear wave velocity obtained by downhole tests and SPT-N values were studied and some correlations were developed. It can be said that the developed correlations show acceptable prediction performance and can be used for similar geotechnical and geological site conditions
