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p(R=rj{m) = probability that given the occurrence of an earthquake of magnitude <br /> m; on source n, rj is the closest distance increment from the rupture <br /> surface to the site; <br /> p(Z>z i m;,rj) = probability that given an earthquake of magnitude m; at a distance <br /> of rj, the ground motion exceeds the specified level z. <br /> The calculations were made using our computer programs XCEED and EXPOSE <br /> (Woodward-Clyde Consultants, 1979). <br /> Seismic Source Characterization <br /> Two types of earthquake sources are characterized in this seismic hazard analysis: (1) faults; <br /> and (2) areal source zones. Faults are modeled as three-dimensional fault surfaces and <br /> details of their behavior are incorporated into the source characterization. Areal source <br /> zones are regions where earthquakes are assumed to occur randomly. Seismic sources are <br /> modeled in the hazard analysis in terms of maximum magnitude, geometry, and earthquake <br /> recurrence. <br /> The geometric source parameters for faults include fault location, segmentation model, dip, <br /> and thickness of the seismogenic zone. The recurrence parameters include recurrence model <br /> (exponential and characteristic), recurrence rate (slip rate or average recurrence interval for <br /> the maximum event on a fault or number of events over the minimum magnitude for a source <br /> zone), and slope of the recurrence curve (b-value). Clearly, the geometry and recurrence <br /> are not totally independent. For example, if a fault is modeled with several small segments <br /> instead of large segments, the maximum magnitude is lower, and a given slip rate requires <br /> many more small earthquakes to accommodate a cumulative seismic moment. <br /> For areal sources, only the maximum magnitude, areas and recurrence need to be defined. <br /> Uncertainties in the source parameters are included in the hazard model using logic trees <br /> (Figure 1). In the logic tree approach, discrete values of the source input parameters have <br /> been included along with our estimate of the likelihood that the discrete value represents the <br /> actual value. Generally all input parameters have been represented by three values: a <br /> H:\CONTRACT'\TENMILE\4 4 M0412951500 <br />