Development of Surface Level Seismic Hazard Maps Considering Local Soil Conditions for the State of Haryana, India

Abstract

An extensive ground response analysis has been carried out in order to consider the effect of local soil conditions on surface level strong ground motions in the state of Haryana, India. Non-linear approach has been adopted to analyze 81 sites drilled up to refusal covering the entire state. It has been observed that 75 sites fall under site class D (medium dense soils), 4 sites under site class C (very dense soils), whereas only 2 sites fall under site class E (loose soils) as per the provisions of National Earthquake Hazard Reduction Program (NEHRP). For the estimation of low strain shear modulus (Gmax) using SPT N-value for different type of soils, various correlations have been used due to non-availability of insitu measured values of shear wave velocity (Vs). The standard backbone curves for clays and sands have been used in the study in the absence of site-specific shear modulus degradation and damping ratio curves. The recorded acceleration time histories of the Ms 7.0 1991 Uttarkashi earthquake, having a focal depth of 10 km with PGA (g) ranging from 0.05g to 0.31g, have been used as input motion for the analysis. Amplification factors for peak ground acceleration (PGA) and spectral acceleration (Sa) for site class D have been calculated which are found to be comparable with those reported in NEHRP provisions. However, the sitespecific hazard parameters determined for the tectonic setup of the seismic study region are quite different from that suggested by Indian standard code of practice.