San Gregorio Fault

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

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 the Pacific Ocean just south of 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 4–10 mm/year (0.2–0.4 inch/year). The most recent major earthquake along the fault had an estimated magnitude of 7 to 7.25 and occurred after 1270 AD—the earliest calibrated radiocarbon date for a native Californian cooking hearth at the Seal Cove site near Moss Beach that shows signs of displacement—but before 1775, when Spanish missionaries arrived in northern California and recorded history began for the region.^[2]

Portions of the fault that come ashore near the cliffs between Pillar Point and Moss Beach are sometimes referred to as "Seal Cove Fault" in the geological literature.^[2]

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^ 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.
^ ^a ^b 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. Bibcode:1997BuSSA..87.1158S. doi:10.1785/BSSA0870051158. S2CID 55708626. Retrieved 18 September 2018.

v t e Seismically active fault zones and tectonic blocks of California
Statewide Faults	San Andreas Fault Salinian Block
Southern California	Brawley Seismic Zone Chino Fault Elsinore Fault Zone Elysian Park Fault Garlock Fault Hollywood fault Hosgri Fault Imperial Fault Zone Laguna Salada Fault Newport–Inglewood Fault Northridge Blind Thrust Fault Peninsular Ranges Puente Hills Fault Raymond Fault Rose Canyon Fault Salton Trough San Cayetano Fault San Diego Trough Fault Zone San Felipe Fault Zone San Gabriel Fault San Jacinto Fault Zone Santa Maria River Fault Santa Ynez Fault Shoreline Fault Sierra Madre Fault Zone Ventura Fault White Wolf Fault Whittier Fault Yorba Linda Fault
Northern California	Bartlett Springs Fault Calaveras Fault Clayton-Marsh Creek-Greenville Fault Concord Fault Hayward Fault Zone Healdsburg Fault Maacama Fault Mendocino Fracture Zone Mendocino Triple Junction Mount Diablo Thrust Fault Monta Vista Fault Nacimiento Fault Pleasanton Fault Rinconada Fault San Gregorio Fault San Pablo Fault Seal Cove Fault Serra Fault Silver Creek Fault Tesla Fault West Napa Fault
Sierra Nevada	Death Valley Fault Zone Furnace Creek Fault Zone Honey Lake Fault Zone Kern Canyon Fault Maria fold and thrust belt Owens Valley Fault Rescue Lineament-Bear Mountains fault zone Sierra Nevada Batholith Sierra Nevada Fault Sierra Nevada-Great Valley Block Smartville Block Walker Lane
Category California Geological Survey Seismic Hazards Mapping Act Mexico (list)

This page was last edited on 29 January 2024, at 08:54

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