1996-02-06_GENERAL DOCUMENTS - M1977493

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Using this relationship and the relative frequency of different magnitude events from the recurrence model, the slip rate can be used to estimate the absolute frequency of different magnitude events. The average return time for the characteristic or maximum magnitude earthquake defines the high magnitude (low likelihood) end of the recurrence curve. When combined with the relative frequency of different magnitude events from the recurrence model, the recurrence curve is established. Attenuation Relationships To characterize the ground motions at a specified site as a result of the seismic sources considered in the probabilistic seismic hazard analysis, empirical attenuation relationships for peak horizontal acceleration are used. Such relationships have been developed from strong motion records from past earthquakes. The strong motion data typically are analyzed statistically in a regression analysis to develop relationships between the ground motion value, distance from the earthquake to the recording station, and magnitude of the earthquake. Other parameters used in these relationships often include the style of faulting and the soil conditions at the recording site. Given a maximum magnitude and source-to-site distance for specific seismic sources, published attenuation relationships can be used to define the median, and ± one standard deviation (16th and 84th percentile) ground motions for a site. The attenuation relationships used in this study were selected on the basis of the appropriateness of the site conditions and tectonic environment for which they were developed. The relationships selected generally represent recent efforts in modeling strong ground motion on the basis of empirical data, although many of the relationships employ theoretical arguments to constrain some of the model parameters. HACONTRAMTENMILE\7 7 M0412951500