San Gregorio Fault

The San Gregorio Fault is an active, 209 km (130 mi) long fault located off the coast of Northern California. The southern end of the fault is in southern Monterey Bay, and the northern end is about 20 km northwest of San Francisco, near Bolinas Bay, where the San Gregorio intersects the San Andreas Fault. Most of the San Gregorio fault trace is located offshore beneath the waters of Monterey Bay, Half Moon Bay, and the Pacific Ocean, though it cuts across land near Point Año Nuevo and Pillar Point. The San Gregorio Fault is part of a system of coastal faults which run roughly parallel to the San Andreas.[1] The movement of the San Gregorio is right-lateral strike-slip, and the slip rate is estimated to be 4 to 10 mm/year (0.2 to 0.4 inch/year). The most recent major earthquake along the fault occurred some time between 1270-1775 AD, with an estimated magnitude of 7 to 7.25.[2]

U.S. Geological Survey map showing the trace of the San Gregorio Fault in yellow, lower center.

References
  1. Brown, Jr., R. D. (1990). "Quaternary deformation". The San Andreas Fault System, California – USGS Professional Paper 1515. United States Geological Survey. p. 89. ISBN 978-0607716269.
  2. Simpson, Gary D.; Thompson, Stephen C.; Noller, J. Stratton; Lettis, William R. (October 1997). "The Northern San Gregorio Fault Zone: Evidence for the Timing of Late Holocene Earthquakes near Seal Cove, California". Bulletin of the Seismological Society of America. 87 (5): 1158–1170. Retrieved 18 September 2018.
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