Seismic Scenario Specific Ground Motion Simulations Consistent With Ground Motion Prediction Equation

Abstract eng:
In seismic hazard analysis ground motion prediction equations (GMPEs) play a pivotal role. For that reason, there are many such GMPEs available for different regions. However, GMPEs provide elastic spectral quantities or other ground motion intensity measures. They do not give any temporal waveform information of ground motions, which is needed for carrying out nonlinear time-history analyses in order to obtain statistical estimates for the structural response. Nevertheless, hazard posed at a given site is usually characterized by elastic spectral quantities from a suitable GMPE. However, no methods are presently available to get ensemble of simulated motions strictly compatible to any target GMPE so that the detailed statistical analysis directly at the response level can be carried out while still being consistent to the hazard posed at that site. A new method is proposed here to characterize the time-frequency characteristics of ground motions via instantaneous energy arrival of wavelet coefficients. Further, the energy arrival patterns are extracted from ground motions corresponding to different magnitudes, source to site distances and local site conditions, and a scaling model for energy arrival pattern based on seismological parameters is developed. Thus, energy arrival patterns for a given seismic scenario are estimated considering their inherent uncertainty and using a proposed reconstruction procedure an ensemble of ground motions for that scenario is simulated. It is found that the median of the linear spectra obtained from such a simulated ensemble is comparable with that obtained independently from a GMPE developed for the same ground motion database. A new method is also proposed by which the energy arrival curves are modified such that the median and standard deviation of linear spectra obtained from the simulated ensemble will closely match those from the target GMPE. In the present study a scaling model for pseudo spectral velocity (PSV) spectrum for 5% damping is considered as the target GMPE. The GMPE-compatible ensemble is found to be in good agreement with the PSV scaling model in terms of median and standard deviation of response spectra. It is further found that the same GMPE-compatible ensemble, developed for 5% damping PSV spectrum, remains naturally consistent with PSV scaling models developed for a wide range of damping ratio provided, all the PSV scaling models are developed using the same ground motion database.

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