Short-term variations in slip rate and size of prehistoric earthquakes during the past 2000 years on the northern San Jacinto fault zone, a major plate-boundary structure in southern California

Most of the displacement across the North American-Pacific plate boundary in southern California is accommodated by the San Jacinto and the southern San Andreas fault zones. If and how the rate of displacement across these fault zones varies along strike and through time are still being resolved. Here, we present four calculations of late Holocene slip rate and average slip per event from the Claremont fault of the northern San Jacinto fault zone that show variations in strain distribution over the past 2000 yr and illustrate how plate-boundary displacement is distributed between the San Jacinto and southern San Andreas fault zones. We calculate a slip rate of 12.8-18.3 mm/yr and an average slip per event of 2.5 m from two measurements of streams offset by 9-11 earthquakes in the past 1500-2000 yr. Faster slip rates of 21-30 mm/yr and an average slip per event of 2.7-3 m were determined from measurements of a stream and a buried channel that were offset by three earthquakes in the past 400-500 yr.