Dynamic response variability of near-surface soil layer due to stochastic material properties

The spatially dynamic response variability of near-surface soil layer during earthquake has been so far inferred mainly from the observation records of closely;spaced seismic arrays. On the dynamic response variability, this study investigates the influence of laterally heterogeneous soil properties by means of first-order perturbation (FOP) and stochastic finite element (SFE) techniques. The theoretical FOP solution is derived first as a frequency-wave number power spectrum. The SFE analysis is then conducted much more effectively by proposing the assumption of the spatial ergodicity. Then, this study shows that the response variability due to the soil heterogeneity is significant over the first predominant frequency of a building site. By using the frequency-dependent correlation distance proposed as a simple measure characterizing the response variability, this study also demonstrates that, within the extent of the heterogeneity published, the FOP analysis is practicallyavailable for the site approximated well as a single soil layer.