Incorporation of envelope delays and amplifications into simulation of far-field long-period ground motions

Abstract

Far-field long-period ground motions (long-period ground motions) are likely to excite significant responses from high-rise buildings. A method for performing stochastic long-period simulations that incorporate envelope delays and basin-induced amplifications is developed, improving upon the conventional point-source model, which generates ground motions without considering nonstationary properties or basin effects. A model for envelope delays is proposed to realize nonstationary properties and empirical amplifications obtained from attenuation relationships account for basin effects. Then, numerical simulations are performed to validate the feasibility of the proposed method by comparing the simulations with records. Furthermore, the parameters related to envelope delays are obtained as the result of fitting by proposed model to the records, and these parameters are treated as random variables represented by probabilistic models. The formulation of basin-induced amplification factors is established on the basis of an impedance ratio relating the site properties at shallow depths to those extending to the top of bedrock. Therefore, a parametric method for simulating long-period ground motions is developed to promote its applications in engineering practice.