Soil improvement and earthquake-induced damage assessment are key issues in geotechnical engineering, both highly dependent on ground motion characteristics. Ground motion at a specific site is strongly influenced by subsurface conditions and soil deposits; hence, an accurate understanding of geotechnical and geological properties is essential for predicting seismic behavior. Among the most critical parameters in this context is the shear wave velocity (Vs), which not only serves as a key geotechnical index but also represents a primary input in seismic site response analyses. Direct determination of Vs through in-situ or laboratory geophysical tests is often costly and time-consuming. Therefore, indirect estimation methods based on correlations between Standard Penetration Test (SPT) results and Vs are widely applied in practice. In this study, based on geotechnical data collected from the Ramsar region in northern Iran, empirical correlations were developed between shear wave velocity and the corrected SPT blow count (N₆₀). The Vs values were indirectly estimated from soil stiffness parameters, including shear modulus and density, obtained from geotechnical laboratory and logging data.

. The derived equations are VS=45.86(N60)0.49 for all soils, VS=69.97(N60)0.29 for fine-grained soils, and VS=57.08(N60)0.44 for coarse-grained soils. The proposed relationships show good agreement with existing correlations for regions with similar soil texture and gradation characteristics, confirming their reliability for preliminary site characterization.