Site Amplification Functions for Central and Eastern North America – Part II: Modular Simulation-Based Models

Abstract

Site amplification models for Central and Eastern North America are developed from simulation results presented in a companion paper. Linear and nonlinear amplification functions are developed for response spectral (RS) accelerations and smoothed Fourier amplitude spectra (FAS). Linear RS model components include ground motion scaling with 30 m time-averaged shear wave velocity ( VS30 scaling) and the effects of site period and sediment depth. These models are modular and can be used with or without period or depth terms. Including these terms, especially site period, is desirable and improves model estimation. Modularity also allows linear and nonlinear amplification terms to be developed and combined with linear amplification models without bias. Nonlinear RS models reduce linear amplification as VS30 decreases and the intensity of rock outcrop motions increases. Linear FAS models are tabulated amplification values as functions of VS30 and depth; nonlinear FAS models are analogous to those for the RS. A linear model for correcting a VS30 = 760 m/s rock condition to VS = 3,000 m/s is produced.