Title: Comment on "Empirical-Stochastic Ground-Motion Prediction for Eastern North America" by Behrooz Tavakoli and Shahram Pezeshk
Abstract: Tavakoli and Pezeshk (2005) conclude that the use of a point-source single-corner source spectrum by Campbell (2003, 2004) causes his eastern North America (ENA) hybrid empirical ground-motion model to underestimate ground-motion amplitudes from near-source large-magnitude earthquakes. This conclusion was based on published studies that found that the use of a double-corner source spectrum, together with a focal depth that increases with magnitude, was required to match a dataset of strong-motion recordings from moderate-to-large earthquakes in California (Atkinson and Silva, 1997, 2000). Tavakoli and Pezeshk also note that Atkinson and Boore (1995, 1997) propose the use of a double-corner source spectrum to model the source spectra of large earthquakes in ENA. These studies lead Tavakoli and Pezeshk to suggest that using a double-corner source spectrum with Campbell’s (2003) hybrid empirical method (HEM) constitutes an improvement in the method.
One of the attributes of the HEM is that the regional adjustment factors that are used to modify the ground-motion estimates in the host region are not sensitive to the exact form of the source spectra or to the absolute amplitudes and functional relationships of the seismological parameters that are used to define the seismological models in the host and target regions. Instead, these adjustment factors are sensitive only to the differences in the seismological models between these regions. This means that the seismological models do not need to produce correct absolute ground-motion amplitudes, as assumed by Tavakoli and Pezeshk; they only need to provide an accurate ratio of ground-motion amplitudes. Accurate ratios will be obtained if the source spectra and the other seismological parameters in each region have the same functional relationships regardless of what form these relationships might take. For example, using a constant stress drop in each region will produce the same regional adjustment factors as using …
Publication Year: 2008
Publication Date: 2008-08-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 3
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