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system. The results of this evaluation indicate that the fault system is capable of generating maximum earthquakes ranging in magnitude from 6.0 to 6.5 (Borchardt, et al., 1972; Woodward -Clyde Consultants, 1977). In addition to evaluating the historic earthquake record, the earthquake potential of faults may be evaluated by applying empirical relationships that relate various fault parameters (e.g., fault length, fault type, etc.) to maximum credible earth- quake (MCE) magnitude. For this study. relationships published in Slemmons (1977) and Slemmons and Chung (1982) were applied to the previously identified faults. The resulting MCE estimates are summarized in Appendix A. For the faults of the Sierran Foothills fault system (Bear Mountains and Melones fault zones), the MCE estimates are in agreement with those of Borchardt (1972) and Woodward -Clyde Consultants (1977), presented previously. While MCE esti- mates for the other faults listed in the table are slightly higher, they are at greater distances from the site and, therefore, are unlikely to produce design ground ac- celerations at the site. To measure the maximum probable earthquake (MPE) during a 100 -year interval as required by Subchapter 15, both the size of potential earthquakes and the av- erage frequency at which they occur (i.e., mean recurrence interval) must be considered. For the Sierran Foothills fault system, the historic earthquake record is of insufficient length to estimate the recurrence interval for significant earth- quakes. The work of previous researchers has resulted in estimates of recur- rence intervals for faults in the Sierran Foothills fault system ranging from 100 to greater than 10,000 years (Hart, et al., 1984). These values compare favorably with recurrence intervals estimated using relationships of earthquake magnitude and fault slip rates which are published in Slemmons and Chung (1982).- Avail- able slip -rate data are limited (Clark, et al., 1984) and suggest that the MCEs for the fault system (magnitude 6.5) are characterized by long recurrence intervals ranging from 6,000 to 800,000 years. This suggests that the probability of having the MCE on the Sierran Foothills fault system in the next 100 years is relatively low. To develop an MPE estimate for the Bear Mountains and Melones fault zones, a probabilistic analysis was conducted using relationships developed by Kiremid- PJ9 9390218A.00W 24 Rev. 0 July 20, 1989