Abstract

The slip rate of the San Andreas fault 45 km north of San Francisco at Olema, California, is determined by matching offset segments of a buried late Holocene stream channel. Stream deposits from 1800 ±78 yr B.P. are offset 42.5 ±3.5 m across the active (1906) fault trace for a minimum late Holocene slip rate of 24 ±3 mm/yr. When local maximum coseismic displacements of 4.9 to 5.5 m from the 1906 earthquake are considered with this slip rate, the recurrence of 1906-type earthquakes on the North Coast segment of the San Andreas fault falls within the interval of 221 ±40 yr. Both comparable coseismic slip in 1906 and similar late Holocene geologic slip rates at the Olema site and a site 145 km northwest at Point Arena (Prentice,1989) suggest that the North Coast segment behaves as a coherent rupture unit.

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