Three-Dimensional Investigation of a 5 m Deflected Swale along the San Andreas Fault in the Carrizo Plain

Handle URI:
http://hdl.handle.net/10754/346782
Title:
Three-Dimensional Investigation of a 5 m Deflected Swale along the San Andreas Fault in the Carrizo Plain
Authors:
Akciz, S. O.; Ludwig, L. G.; Zielke, Olaf; Arrowsmith, J. R.
Abstract:
Topographic maps produced from Light Detection and Ranging (LiDAR) data are useful for paleoseismic and neotectonic research because they provide submeter representation of faulting-related surface features. Offset measurements of geomorphic features, made in the field or on a remotely sensed imagery, commonly assume a straight or smooth (i.e., undeflected) pre-earthquake geometry. Here, we present results from investigation of an ∼20 cm deep and >5 m wide swale with a sharp bend along the San Andreas fault (SAF) at the Bidart fan site in the Carrizo Plain, California. From analysis of LiDAR topography images and field measurements, the swale was initially interpreted as a channel tectonically offset ∼4:7 m. Our observations from exposures in four backhoe excavations and 25 hand-dug trenchettes show that even though a sharp bend in the swale coincides with the trace of the A.D. 1857 fault rupture, the swale formed after the 1857 earthquake and was not tectonically offset. Subtle fractures observed within a surficial gravel unit overlying the 1857 rupture trace are similar to fractures previously documented at the Phelan fan and LY4 paleoseismic sites 3 and 35 km northwest of Bidart fan, respectively. Collectively, the fractures suggest that a post-1857 moderate-magnitude earthquake caused ground cracking in the Carrizo and Cholame stretches of the SAF. Our observations emphasize the importance of excavation at key locations to validate remote and ground-based measurements, and we advocate more geomorphic characterization for each site if excavation is not possible.
KAUST Department:
Physical Sciences and Engineering (PSE) Division
Citation:
Three-Dimensional Investigation of a 5 m Deflected Swale along the San Andreas Fault in the Carrizo Plain 2014, 104 (6):2799 Bulletin of the Seismological Society of America
Publisher:
Seismological Society of America
Journal:
Bulletin of the Seismological Society of America
Issue Date:
21-Oct-2014
DOI:
10.1785/0120120172
Type:
Article
ISSN:
0037-1106
Additional Links:
http://www.bssaonline.org/cgi/doi/10.1785/0120120172
Appears in Collections:
Articles; Physical Sciences and Engineering (PSE) Division

Full metadata record

DC FieldValue Language
dc.contributor.authorAkciz, S. O.en
dc.contributor.authorLudwig, L. G.en
dc.contributor.authorZielke, Olafen
dc.contributor.authorArrowsmith, J. R.en
dc.date.accessioned2015-03-17T13:55:59Zen
dc.date.available2015-03-17T13:55:59Zen
dc.date.issued2014-10-21en
dc.identifier.citationThree-Dimensional Investigation of a 5 m Deflected Swale along the San Andreas Fault in the Carrizo Plain 2014, 104 (6):2799 Bulletin of the Seismological Society of Americaen
dc.identifier.issn0037-1106en
dc.identifier.doi10.1785/0120120172en
dc.identifier.urihttp://hdl.handle.net/10754/346782en
dc.description.abstractTopographic maps produced from Light Detection and Ranging (LiDAR) data are useful for paleoseismic and neotectonic research because they provide submeter representation of faulting-related surface features. Offset measurements of geomorphic features, made in the field or on a remotely sensed imagery, commonly assume a straight or smooth (i.e., undeflected) pre-earthquake geometry. Here, we present results from investigation of an ∼20 cm deep and >5 m wide swale with a sharp bend along the San Andreas fault (SAF) at the Bidart fan site in the Carrizo Plain, California. From analysis of LiDAR topography images and field measurements, the swale was initially interpreted as a channel tectonically offset ∼4:7 m. Our observations from exposures in four backhoe excavations and 25 hand-dug trenchettes show that even though a sharp bend in the swale coincides with the trace of the A.D. 1857 fault rupture, the swale formed after the 1857 earthquake and was not tectonically offset. Subtle fractures observed within a surficial gravel unit overlying the 1857 rupture trace are similar to fractures previously documented at the Phelan fan and LY4 paleoseismic sites 3 and 35 km northwest of Bidart fan, respectively. Collectively, the fractures suggest that a post-1857 moderate-magnitude earthquake caused ground cracking in the Carrizo and Cholame stretches of the SAF. Our observations emphasize the importance of excavation at key locations to validate remote and ground-based measurements, and we advocate more geomorphic characterization for each site if excavation is not possible.en
dc.publisherSeismological Society of Americaen
dc.relation.urlhttp://www.bssaonline.org/cgi/doi/10.1785/0120120172en
dc.rightsArchived with thanks to Bulletin of the Seismological Society of Americaen
dc.titleThree-Dimensional Investigation of a 5 m Deflected Swale along the San Andreas Fault in the Carrizo Plainen
dc.typeArticleen
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
dc.identifier.journalBulletin of the Seismological Society of Americaen
dc.eprint.versionPublisher's Version/PDFen
dc.contributor.institutionProgram in Public Health, University of California–Irvine, Irvine, California 92697en
dc.contributor.institutionSchool of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287en
dc.contributor.institutionNow at Department of Earth, Planetary and Space Sciences, University of California, Los Angeles, California 90095.en
dc.contributor.affiliationKing Abdullah University of Science and Technology (KAUST)en
kaust.authorZielke, Olafen
All Items in KAUST are protected by copyright, with all rights reserved, unless otherwise indicated.