Correlation between Shear Wave Velocity (Vs) and corrected SPT-N for Bharuch Region of Gujarat, India

The assessment of ground motion during an earthquake depends on the shear wave velocity (Vs) of the existing soil strata. The Vs determines the characteristics of soil layer under earthquake motion at a given site. However, the Vs profile of a particular region is not readily available. The correlations of Vs with standard penetration (SPT) resistance can be of significant importance in such conditions. The present study discusses the development of a correlation between Vs measured by multi-channel analysis of surface waves (MASW) testing and corrected N value measured by SPT at various sites in the Bharuch region of Gujarat, India (located in seismic zone III). These tests were carried out at nine locations within a twenty-kilometer radius of the Bharuch region. An empirical correlation between Vs and corrected N was developed based on statistical assessments. The regression coefficient (R²) value of Vs with corrected N was found to be 0.8752. At each site, roll-along MASW tests were carried out to estimate the two-dimensional (2D) Vs profile using spatial resolution techniques. According to the NEHRP guidelines, these sites were classified as C and D based on Vs30 computed from 1D Vs profile using the MASW technique. The proposed relationships can be helpful in seismic microzonation and seismic hazard analysis of this earthquake-prone region.