Probabilistic assessment of ground motions intensity considering soil properties uncertainty

This paper aims to evaluate the effects of soil uncertainty and soil depth to bedrock on the ground motions intensity. For this, three different depths are considered and the variability of the ground motions characteristics traveling from depth to surface is investigated. Soil maximum shear modulus, G0, which mainly controls soil stiffness and strength characteristics is considered as the uncertain soil material property. By employing the Monte Carlo (MC) simulation technique and for a defined soil depth, the effect of G0 variability on the ground motions intensity is investigated. Furthermore, the accuracy of approximate method of First Order Second Moment (FOSM) for response variability estimation is evaluated. Using an approximate method is important because probabilistic analysis methods are commonly very time consuming. By conducting investigations, it's observed that the seismic responses of soil domain including PGA, Amplification Factor (AF) and spectral responses of Single Degree Of Freedom (SODF) system are strongly dependent on the soil depth. Moreover, by comparing the results of FOSM with MC, it is observed that FOSM is able to estimate the responses' variability with acceptable accuracy. Thus, FOSM method could be reasonably used instead of MC simulation technique for predicting the seismic response of the soil domain considering soil G0 uncertainty.