STUDY AND APPLICATION OF STOCHASTIC GROUND MOTION MODELLING AND SIMULATION

Abstract

ABSTRACT A fully nonstationary stochastic model for strong earthquake ground motion has been taken for study. The model employs filtering of a discretized white-noise process. Nonstationarity is achieved by modulating the intensity and varying the filter properties in time. The formulation has the important advantage of separating the temporal and spectral nonstationary characteristics of the process, thereby allowing flexibility and ease in modeling and parameter estimation. The model is fitted to target ground motions by matching a set of statistical characteristics, including the mean-square intensity, the cumulative mean number of zero-level up-crossings and a measure of the bandwidth, all expressed as functions of time. Post-processing by a second filter assures zero residual velocity and displacement, and improves the match to response spectral ordinates for long periods. Hence, together with the target accelerogram, they can be considered as realizations of a stochastic ground motion having the characteristics of the earthquake and site, which produced the target motion. Such an ensemble of ground motions would be appropriate for design or assessment of a structure for that particular earthquake. However, in the broader context of PBEE (performance based earthquake engineering) design and analysis associated with the structure, an ensemble of ground motions that represents all possible earthquakes at a site is of interest.