Parametric Statistical Generalization of Uniform-Hazard Earthquake Ground Motions

Abstract

Sets of ground-motion records used for seismic hazard analyses typically have intensity measures corresponding to a particular hazard level for a site (perhaps conditioned on a particular intensity value and hazard). In many cases the number of available ground motions that match required spectral ordinates and other criteria (such as duration, fault rupture characteristics, and epicentral distance) may not be sufficient for high-resolution seismic hazard analysis. In such cases it is advantageous to generate additional ground motions using a parameterized statistical model calibrated to records of the smaller data set. This study presents a statistical parametric analysis of ground-motion data sets that are classified according to a seismic hazard level and a geographic region and that have been used extensively for structural response and seismic hazard analyses. Parameters represent near-fault effects such as pulse velocity and pulse period, far-field effects such as velocity amplitude and power-spectral attributes, and envelope characteristics. A systematic fitting of parameterized pulse functions to the individual ground-motion records, of parameterized envelopes to individual instantaneous ground-motion amplitudes, and of parameterized power-spectral density functions to averaged power spectra result in probability distributions for ground-motion parameters representative of particular seismic hazard levels for specific geographical regions. This methodology presents a means to characterize the variability in a set of ground-motion records of physically meaningful parameters.