Estimation of Linear Site Amplification by a Ground Motion Prediction Equation Using Results from a Site Survey

One of the ground motion prediction equations (GMPEs), which have recently been developed in the Next Generation Attenuation (NGA) project, is employed in this article to estimate site response in terms of amplification factor of the seismic waves in soft superficial sedimentary layer. This study also presents briefly the existing information dealing with the methods for estimating subsurface shear wave velocities. The discussion about three geophysical methods, one invasive and two noninvasive namely SPSVL, SPAC and HVSR respectively, presents a better identification of their actual possibilities and limitations. The results obtained from a field survey from these three methods are utilized in this article to evaluate linear site amplification. This study can be considered as one of the instances where the limitation, to apply GMPEs in diversified geological conditions, was encountered. Some amendments in the fixed parameters were considered necessary in the original NGA GMPE to get realistic results. The variation in amplifications, obtained in this way, from SPSVL and SPAC method is negligible and their average is 1.33 for a spectral period of 1.1 sec. Some recommendations are furnished to utilize other NGA relations and craft adaptation in them according to the local geologic conditions, if required, to evaluate ground motions for seismic hazard analysis.