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15,1998 • • 983-2348.135 were taken from the available data, or estimated based on the information in the available data, are listed in Table 1. The fault geologic and geometric chazaderistics listed in Table 1 were used to calculate the maximum credible earthquake (MCE) for each potential seismogenic source, using the fault rupture versus eazthquake magnitude relationships of Anderson et al (1996), Wells and Coppersmith (1994), and Slemmons (1982). The MCEs for each source listed in Table 1 were selected from the suite of calculated possible MCEs for each source (derived from the various fault rupture versus magnitude relationships) based prirnarily on the reliability, accuracy and completeness of the available fault rupture geometric and geologic data. In addition, selected source chazacteristics (i.e., total length, rupture length, rupture width, slip rate), along with the MCE for each source were used as input data in the development of the probabilistic assessment of ground motions. The MCE calculation sheets for each of the faults aze included in Attachment 1 The total lengths for the various potential seismogenic sources were taken directly from the available maps and tabulations of Witkind (1976) grid Kirkham and Rogers (1981). Rupture lengths were estimated from the available data based on mapped segment lengths, and the mapped orientations of the faults, as well as from comparisons to analogs in similar tectonic environments. Rupture widths were developed based on the type and estimated geometry of the fault, in conjunction with estimates of the Qustal and seismogenic thickness. Slip rates for the Oil Creek, Ute Pass, Rampart Range and Kennedy faults were calculated using the fault source activity and magnitude pazameters of Butler and Nicholl (1986), and the earthquake magnitude versus fault displacement relationships of Wells and Coppersmith (1994). Slip rates for the remaining sources were estimated based on comparisons of their geologic and age chazacteristics with respect to those of the Oil Creek, Ute Pass, Rampart Range and Kennedy faults. The closest potential seismogenic source to the site is the Oil Creek fault. It is considered to be a normal-slip fault, has a total length of about 58 km (36 mi), and is located about 8 km (5 mi) to the northeast at its closest approach to the site. Its MCE was calculated to be a moment magnitude Mw 6.8. Based on the annual seismicity rate of 0.22E-4 for the maximum earthquake on the Oil Creek fault from Butler and Nicholl (1986), which equates to a recurrence interval of about 45,454 yeazs, and the calculated displacement for the maximum earthquake event on the fault of about 1.2 m (4 ft), based on the relationships of Wells and Coppersmith (1994), the slip rate was calculated to be 0.027 mm/yr. Development of Probabilistic Peak Ground Accelerations The site-specific probabilistic seismic design output for the CC&V Project was established in terms of the peak ground acceleration (PGA) and the return period for the PGA. The return periods that were considered ranged from 100 yeazs to 2,500 years, including a return period of 475 yeazs, which is equivalent to a risk level, and design life Golder Auoelates