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earthquake on the Northern Calaveras in the next 100 years. This earthquake is the same magnitude as the largest historical earthquake on the Calaveras fault and hence the WE is defined by the largest historical earthquake magnitude. The recommended WE is a magnitude 6.6 earthquake at a distance of 96 km. Hayward Fault The Hayward Fault is located 106 km west 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 southern 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 Working Group on Northern California Earthquake Probabilities (WGNCEP,1996) estimated the expected magnitude on the northern and southern segments of the Hayward Fault as M=6.9 with a recurrence interval of 210 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 WE of magnitude 7.0 at a distance of 106 km for the Hayward fault. San Andreas Fault The San Andreas Fault is located approximately 135 km west of the site. The San Andreas Fault is a 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 into the North Coast segement, Peninsula segment, and Santa Cruz Mountains segment. The site is located closest to the northern end of the Santa Cruz Mountains segment.