Effect of uncertainty in \[V_{\mathrm{S}}{-}N\] correlations on seismic site response analysis

This paper studies the reliability of the calculated shear-wave velocity (\[V_{\mathrm{S}}\]) from different available \[V_{\mathrm{S}}\] and SPT-N correlations in terms of seismic site response analysis. In the present study, various \[V_{\mathrm{S}}\]–N correlations developed for different regions around the globe have been used to calculate the bound of \[V_{\mathrm{S}}\] variations with depth at three different sites in Kolkata city. This bound has later been used to generate the random \[V_{\mathrm{S}}\] profiles using the Monte Carlo simulation. Equivalent linear site response analysis has been performed to study the response of those generated profiles under different input motion excitations. Strong-to-weak ground motion records have been used for this purpose. The amplification spectra of the generated \[V_{\mathrm{S}}\] profiles using all soil types and specific soil-type \[V_{\mathrm{S}}\]–N correlations show significant variations. The study also shows that the \[V_{\mathrm{S}}\]–N correlation may result in quite different \[V_{\mathrm{S},30}\] values and subsequently it may lead to the different site classes according to the NEHRP 2003 classification. So, the random choice of the \[V_{\mathrm{S}}\]–N correlation, where the direct measurement of \[V_{\mathrm{S}}\] is not available, may affect the outcome of seismic hazard analysis significantly. The study points out the need for accurate estimation of the \[V_{\mathrm{S}}\] profile either from in-situ determination or using site-specific correlation.