Influence of Variabilities of Input Parameters on Seismic Site Response Analysis

The seismic waves originating from an earthquake source undergoes significant amplification on its way toward the surface. The dynamic properties of the soil such as shear modulus/stiffness degradation and damping play a major role in amplifying the seismic waves. In the present study, two sample bore logs from Calicut have been taken for one-dimensional equivalent linear ground response studies. The bore logs represent clayey and sandy deposits and the shear wave velocity (V_{s (30)}) of these sites are in the range of 300–360 ms⁻¹(NEHRP C). The uncertainty in the soil properties has been addressed by randomizing the soil profile using Monte Carlo simulation on STRATA. Similarly, the influence of the number of ground motions on the site response has been analyzed by considering different ground motion suites. The regional seismic hazard consistent ground motions have been considered for the analysis. The variation of Peak Ground Acceleration (PGA) along the depth of the soil profile is studied to understand the influence of local soil profile in modifying the wave properties. The influence of variability associated with the input parameters has been assessed through numerical experiments considering multiple numbers of realizations (V_s profile) and ground motions. The study reveals the variability associated with the ground motions to be high when compared to soil property. It can be concluded that the uncertainty in the input motion has a significant impact on the overall outcome of site response analysis.