Influence of local site conditions on strong ground motion characteristics at Tarai region of Uttarakhand, India

Abstract

Local site conditions strongly influence the characteristics of strong ground motion. In this study, influence of local site conditions on characteristics of strong ground motion records and their further effects on hazard studies were investigated for the Tarai region of Uttarakhand, India, where the thickness of soil cover varies significantly from few meters to several hundreds of meters. Another importance of these sites is that these sites have strong motion recording stations. Site characterization of each of the strong ground motion station is conducted using MASW tests to obtain shear wave velocity profiles of the sites. Further, site-specific ground response analysis is carried out using SHAKE2000 to investigate local site effects on strong ground motion records. Results clearly show the differences in IS 1893:2002 (Part-1) suggested 5 % damping response spectrum and the one obtained from ground response analyses. For sites having Vs30 around 200 m/s, constant acceleration frequency band is significantly widened in comparison with 5 % damping response spectrum of IS-1893:2002 (Part-1). This study further suggests the importance of thorough site characterization of strong motion instrumentation sites.