Simulation of synthetic ground motions for specified earthquake and site characteristics

Abstract

SUMMARYA method for generating a suite of synthetic ground motion time-histories for specified earthquake and site characteristics defining a design scenario is presented. The method employs a parameterized stochastic model that is based on a modulated, filtered white-noise process. The model parameters characterize the evolving intensity, predominant frequency, and bandwidth of the acceleration time-history, and can be identified by matching the statistics of the model to the statistics of a target-recorded accelerogram. Sample 'observations' of the parameters are obtained by fitting the model to a subset of the NGA database for far-field strong ground motion records on firm ground. Using this sample, predictive equations are developed for the model parameters in terms of the faulting mechanism, earthquake magnitude, sourceto-site distance, and the site shear-wave velocity. For any specified set of these earthquake and site characteristics, sets of the model parameters are generated, which are in turn used in the stochastic model to generate the ensemble of synthetic ground motions. The resulting synthetic acceleration as well as corresponding velocity and displacement time-histories capture the main features of real earthquake ground motions, including the intensity, duration, spectral content, and peak values. Furthermore, the statistics of their resulting elastic response spectra closely agree with both the median and the variability of response spectra of recorded ground motions, as reflected in the existing prediction equations based on the NGA database. The proposed method can be used in seismic design and analysis in conjunction with or instead of recorded ground motions.

Predictive model for site specific simulation of ground motions based on earthquake scenarios

“…Constant damping ratio of the ground motion has also been used by Rezaeian et al 24 following a different time-domain based approach.…”

“…Predictive relations are then developed in the form of linear mixed-effects normal regression models, capable of linking the translated model parameters to typically used earthquake and site-dependent ground motion predictors, similar to GMPEs developments 5,6 and earlier works in the literature. 24,28 The predictors that are chosen to describe an earthquake scenario are the earthquake moment magnitude M w , the closest-to-ruptured-area distance R rup , and the average shear-wave velocity V S 30 at the site of interest. The random terms in the developed linear mixed regression models, typically referred to as random effects, can model effectively the correlation of ground motions pertaining to the same seismic event, while considering at the same time the fact that each different site is expected to have its own effect on the resulting ground motion.…”

“…Despite the fact that there is no precedent for analytical expressions describing the attenuation of these specific normal K-T model parameters, one may anticipate that the transformed normal parameters Z i would scale in a similar manner to other seismic ground motion measures as in the GMPEs studies, 5-7 the stationary FAS 10 in the NGA-East project, 8 or other previous works in the literature for the parametrization and stochastic simulation of ground motions consistent with an earthquake scenario. 24,28 Numerous candidate functional forms have been considered, partly inspired by the aforementioned works, and the relative performance of each candidate form has been evaluated with respect to several commonly used statistical measures, such as the Akaike Information Criterion, the Bayesian Information Criterion, the variance of the residual components and the pattern of the residual error plots. A single functional form for the predictive regressions of all transformed normal model parameters has been chosen, in a effort to perform their statistical modeling in a unified and consistent way, while facilitating at the same time their simulation process.…”

“…These findings are generally consistent with seismological evidence [46][47][48][49][50][51][52] and prior works in the literature. 24 Representative diagnostic scatter plots of residual components against the chosen earthquake and local site characteristics, moment magnitude M, closest-to-ruptured-area distance R (in km) and local site average shear-wave velocity V (in m/s), are provided in Figure 3 for the transformed standard normal model parameters {Q 1 , 1 , 1 } that collectively define the first dominant modal frequency, the first modal apparent damping ratio (1) g , the total energy content I x , and the duration T d of the seismic ground motion. The provided scatter plots illustrate the fact that the estimated residual components are unbiased, exhibit variance homogeneity and lack any patterning with respect to the used ground motion physical predictors, further supporting the appropriateness of the developed regression expression.…”

Novel procedure for reliability-based cost optimization of seismically isolated structures for the protection of critical equipment: A case study using single curved surface sliders

“…The temporal nonstationarity arises from the transient nature of the earthquake event whereas the spectral nonstationarity of the ground motion arises from the evolving nature of the seismic waves arriving at a site. [46] The filtered random white noise is the response of a time-variant filter subjected to the white noise excitation. The time variant filter is itself the impulse response function of a single degree of freedom system having time-variant natural frequency and damping.…”