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Source, Path, and Site Ground Motion Model of the Loma Prieta Earthquake: Preliminary Results

by W. Silva and C. Stark

Silva, W., and C. Stark (1991). Source, Path, and Site Ground Motion Model of the Loma Prieta Earthquake: Preliminary Results. SMIP91 Seminar on Seismological and Engineering Implications of Recent Strong-Motion Data, p. 1-1 - 1-11.

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Abstract

The objective of this study is to model the observed strong ground motion variability during the 1989 Loma Prieta earthquake. The modeling exercise is intended to assess the effects of source finiteness, crustal propagation, and site response upon the recorded motions. The ground motion model employed combines a model for the finite earthquake source as well as nonlinear soil response and crustal propagation effects with the band-limited-white-noise (BLWN) ground motion model. The combined model uses random vibration theory (RVT) to produce site specific estimates of peak acceleration and response spectral ordinates. Preliminary results indicate that the simple point-source using a 1/distance geometrical attenuation provides the optimum overall fit to observed response spectra at fault distances ranging from 1 - 80 km. In addition, knowledge of site specific kappa values reduce the uncertainty in spectral estimates for frequencies exceeding 3 - 4 Hz.