Probabilistic Site Identification Analysis Using NUPEC Recorded Free-Field Motions

This paper describes a probabilistic site identification analysis performed by BNL, using the free-field earthquake motions recorded at the NUPEC test site. The BNL analysis was intended to provide adequate characterization of the soil properties for the test site to be used for the SSI analyses. The free-field data were provided by NUPEC. The methodology employed in the BNL probabilistic analysis of site identification includes the Monte Carlo process in conjunction with equivalent linear convolution analyses for generating a large number of site profiles for use in convolution studies from which mean estimates of response can be generated. The random variable selected to characterize the site profile is the shear wave velocity in each soil layer of the site profile. A lognormal distribution was assumed with the standard deviation determined from available site data and applicable regulatory requirements. The convolution analyses were performed using an appropriate soil degradation model and the outcrop input motions generated from the recorded in-rock motions. The BNL analysis produced results in terms of the mean, median and various fractiles of free-field soil properties at the test site, and the corresponding surface response spectra, which are presented in this paper.