Topographic gradient based site characterization in India complemented by strong ground-motion spectral attributes

highlights
• Appraised the topographic-gradient approach for first-cut evaluations of site conditions.
• Reported site classification support of the viability of the approach.
• Techniques based on strong ground motion recordings are also experimented to support the efficacy of the site classification derived based on topographic-gradients.

We appraise topographic-gradient approach for site classification that employs correlations between 30 m column averaged shear-wave velocity and topographic gradients. Assessments based on site classifications reported from cities across India indicate that the approach is reasonably viable at regional level. Additionally, we experiment three techniques for site classification based on strong ground-motion recordings, namely Horizontal-to-Vertical Spectral Ratio (HVSR), Response Spectra Shape (RSS), and Horizontal-to-Vertical Response Spectral Ratio (HVRSR) at the strong motion stations located across the Himalayas and northeast India. Statistical tests on the results indicate that these three techniques broadly differentiate soil and rock sites while RSS and HVRSR yield better signatures. The results also support the implemented site classification in the light of strong ground-motion spectral attributes observed in different parts of the globe.