Dataset Identification:
Resource Abstract:
- description: This part of DS 781 presents data for folds for the geologic and geomorphic map of the Offshore of Pacifica map
area, California. The vector data file is included in "Folds_OffshorePacifica.zip," which is accessible from http://pubs.usgs.gov/ds/781/OffshorePacifica/data_catalog_OffshorePacifica.html.
The Offshore of Pacifica map area straddles the right-lateral transform boundary between the North American and Pacific plates
and is cut by several active faults that cumulatively form a distributed shear zone, including the San Andreas Fault, the
eastern strand of the San Gregorio Fault, the Golden Gate Fault, and the Potato Patch Fault (sheets 8, 9; Bruns and others,
2002; Ryan and others, 2008). These faults are covered by Holocene sediments (mostly units Qms, Qmsb, Qmst) with no seafloor
expression, and are mapped using seismic-reflection data (sheet 8). The San Andreas Fault is the primary plate-boundary structure
and extends northwest across the map area; it intersects the shoreline 10 km north of the map area at Pacifica Lagoon, and
3 km south of the map area at Mussel Rock. This section of the San Andreas Fault has an estimated slip rate of 17 to 24 mm/yr
(U.S. Geological Survey, 2010), and the devastating Great 1906 California earthquake (M 7.8) is thought to have nucleated
on the San Andreas a few kilometers offshore of San Francisco within the map area (sheet 9; Bolt, 1968; Lomax, 2005). The
San Andreas Fault forms the boundary between two distinct basement terranes, Upper Jurassic to Lower Cretaceous rocks of the
Franciscan Complex to the east, and Late Cretaceous granitic and older metamorphic rocks of the Salinian block to the west.
Franciscan Complex rocks (unit KJf, undivided) form seafloor outcrops at and north of Point Lobos adjacent to onland exposures.
The Franciscan is divided into 13 different units for the onshore portion of this geologic map based on different lithologies
and ages, but the unit cannot be similarly divided in the offshore because of a lack of direct observation and (or) sampling.
Folds were primarily mapped by interpretation of seismic reflection profile data (see S-15-10-NC and F-2-07-NC). The seismic
reflection profiles were collected between 2007 and 2010. References Cited Bolt, B.A., 1968, The focus of the 1906 California
earthquake: Bulletin of the Seismological Society of America, v. 58, p. 457€“471. Bruns, T.R., Cooper, A.K., Carlson,
P.R., and McCulloch, D.S., 2002, Structure of the submerged San Andreas and San Gregorio fault zones in the Gulf of Farallones
as inferred from high-resolution seismic-reflection data, in Parsons, T. (ed.), Crustal structure of the coastal and marine
San Francisco Bay region, California: U.S. Geological Survey Professional Paper 1658, p. 77€“117. Lomax, A., 2005,
A reanalysis of the hypocentral location and related observations for the Great 1906 California earthquake: Bulletin of the
Seismological Society of America, v. 95, p. 861€“877. Ryan, H.F., Parsons, T., and Sliter, R.W., 2008. Vertical
tectonic deformation associated with the San Andreas fault zone offshore of San Francisco, California. Tectonophysics, 429
(1-2), p. 209€“224. U.S. Geological Survey and California Geological Survey, 2010, Quaternary fault and fold database
for the United States, accessed April 5, 2012, from USGS website: http://earthquake.usgs.gov/hazards/qfaults/.; abstract:
This part of DS 781 presents data for folds for the geologic and geomorphic map of the Offshore of Pacifica map area, California.
The vector data file is included in "Folds_OffshorePacifica.zip," which is accessible from http://pubs.usgs.gov/ds/781/OffshorePacifica/data_catalog_OffshorePacifica.html.
The Offshore of Pacifica map area straddles the right-lateral transform boundary between the North American and Pacific plates
and is cut by several active faults that cumulatively form a distributed shear zone, including the San Andreas Fault, the
eastern strand of the San Gregorio Fault, the Golden Gate Fault, and the Potato Patch Fault (sheets 8, 9; Bruns and others,
2002; Ryan and others, 2008). These faults are covered by Holocene sediments (mostly units Qms, Qmsb, Qmst) with no seafloor
expression, and are mapped using seismic-reflection data (sheet 8). The San Andreas Fault is the primary plate-boundary structure
and extends northwest across the map area; it intersects the shoreline 10 km north of the map area at Pacifica Lagoon, and
3 km south of the map area at Mussel Rock. This section of the San Andreas Fault has an estimated slip rate of 17 to 24 mm/yr
(U.S. Geological Survey, 2010), and the devastating Great 1906 California earthquake (M 7.8) is thought to have nucleated
on the San Andreas a few kilometers offshore of San Francisco within the map area (sheet 9; Bolt, 1968; Lomax, 2005). The
San Andreas Fault forms the boundary between two distinct basement terranes, Upper Jurassic to Lower Cretaceous rocks of the
Franciscan Complex to the east, and Late Cretaceous granitic and older metamorphic rocks of the Salinian block to the west.
Franciscan Complex rocks (unit KJf, undivided) form seafloor outcrops at and north of Point Lobos adjacent to onland exposures.
The Franciscan is divided into 13 different units for the onshore portion of this geologic map based on different lithologies
and ages, but the unit cannot be similarly divided in the offshore because of a lack of direct observation and (or) sampling.
Folds were primarily mapped by interpretation of seismic reflection profile data (see S-15-10-NC and F-2-07-NC). The seismic
reflection profiles were collected between 2007 and 2010. References Cited Bolt, B.A., 1968, The focus of the 1906 California
earthquake: Bulletin of the Seismological Society of America, v. 58, p. 457€“471. Bruns, T.R., Cooper, A.K., Carlson,
P.R., and McCulloch, D.S., 2002, Structure of the submerged San Andreas and San Gregorio fault zones in the Gulf of Farallones
as inferred from high-resolution seismic-reflection data, in Parsons, T. (ed.), Crustal structure of the coastal and marine
San Francisco Bay region, California: U.S. Geological Survey Professional Paper 1658, p. 77€“117. Lomax, A., 2005,
A reanalysis of the hypocentral location and related observations for the Great 1906 California earthquake: Bulletin of the
Seismological Society of America, v. 95, p. 861€“877. Ryan, H.F., Parsons, T., and Sliter, R.W., 2008. Vertical
tectonic deformation associated with the San Andreas fault zone offshore of San Francisco, California. Tectonophysics, 429
(1-2), p. 209€“224. U.S. Geological Survey and California Geological Survey, 2010, Quaternary fault and fold database
for the United States, accessed April 5, 2012, from USGS website: http://earthquake.usgs.gov/hazards/qfaults/.
Citation
- Title Folds--Offshore of Pacifica map area, California.
-
- creation Date
2018-05-21T09:47:47.485973
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- URL: https://pubs.usgs.gov/ds/781/
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- Description URL provided in Dublin Core references element.
Linkage for online resource
- name Dublin Core references URL
- URL: http://pubs.usgs.gov/ds/781/
- protocol WWW:LINK-1.0-http--link
- link function information
- Description URL provided in Dublin Core references element.
Metadata data stamp:
2018-08-06T19:48:29Z
Resource Maintenance Information
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- notes: This metadata record was generated by an xslt transformation from a dc metadata record; Transform by Stephen M. Richard, based
on a transform by Damian Ulbricht. Run on 2018-08-06T19:48:29Z
Metadata contact
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pointOfContact
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CINERGI Metadata catalog
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- electronic Mail Address cinergi@sdsc.edu
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eng
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standard version:
2007
Metadata record identifier:
urn:dciso:metadataabout:149bea55-70c8-45eb-ab83-d9d6d8bbe5a9
Metadata record format is ISO19139 XML (MD_Metadata)