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about a 1/3 chance of having a magnitude 5.5 earthquake or larger on the Napa Fault in the next 100 years. The recommended MPE is a magnitude 5.5 earthquake at a distance of 89 km. Hayward Fault The Hayward Fault is located 94 km east of the site. The Hayward Fault is often divided into two segments: northern and southern. The southern segment extends from Warm Springs to south of Mills College, a distance of about 32 km. The northern segment extends to from south of Mills College to San Pablo Bay, a distance of 50 km. The site is closest to the northern segment. Many large earthquakes have occurred on the Hayward Fault in the historical record. The largest historical earthquakes associated with the Hayward Fault are the two magnitude 6.8 earthquakes: 1836 and 1868. The 1988 U. S. Geological Survey Working Group on earthquake probabilities in California estimated the expected magnitude on the northern and southern segments of the Hayward Fault as M=7 with a return period of 200 years. Since the last large event was in 1868,the probability that the magnitude 7 event will occur in the next 30 years was estimated at 20% with fair confidence. Using the Working group procedure, I computed the probability that the Hayward Fault will experience a magnitude 7 earthquake during the next 100 years to be about 50%. I recommend using an MPE of magnitude 7.0 at a distance of 94 km for the Hayward Fault. i San Andreas Fault The San Andreas Fault is located approximately 124 km west of the site. This section of the San Andreas Fault is called the North Coast Segment. The San Andreas Fault is a j predominately right-lateral strike-slip fault extending from Cape Mendocino to Mexico. ± The northern and southern sections of the fault are divided by the central creeping section south of Hollister to Parkfield. The northern half of the San Andreas Fault is further segmented near San Francisco.