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Mudflow Generated by Retrogressive Slope Failure, Santa Barbara Basin, California Continental Borderland

1995; Society for Sedimentary Geology; Volume: Vol. 65A; Linguagem: Inglês

10.1306/d4268022-2b26-11d7-8648000102c1865d

1938-3681

Brian Edwards, Homa J. Lee, Michael E. Field,

Groundwater flow and contamination studies

Other| January 02, 1995 Mudflow generated by retrogressive slope failure, Santa Barbara Basin, California continental borderland Brian D. Edwards; Brian D. Edwards U. S. Geological Survey, Menlo Park, CA, United States Search for other works by this author on: GSW Google Scholar Homa J. Lee; Homa J. Lee Search for other works by this author on: GSW Google Scholar Michael E. Field Michael E. Field Search for other works by this author on: GSW Google Scholar Author and Article Information Brian D. Edwards U. S. Geological Survey, Menlo Park, CA, United States Homa J. Lee Michael E. Field Publisher: SEPM Society for Sedimentary Geology First Online: 03 Mar 2017 Online ISSN: 1938-3681 Print ISSN: 1527-1404 GeoRef, Copyright 2006, American Geological Institute. Journal of Sedimentary Research (1995) 65 (1a): 57–68. https://doi.org/10.1306/D4268022-2B26-11D7-8648000102C1865D Article history First Online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Brian D. Edwards, Homa J. Lee, Michael E. Field; Mudflow generated by retrogressive slope failure, Santa Barbara Basin, California continental borderland. Journal of Sedimentary Research 1995;; 65 (1a): 57–68. doi: https://doi.org/10.1306/D4268022-2B26-11D7-8648000102C1865D Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyJournal of Sedimentary Research Search Advanced Search Abstract The morphology and internal geometry of a mudflow deposit on the mainland slope of the Santa Barbara Basin are defined using high-resolution seismic-reflection data in combination with core samples. Sediment failure occurred on a 4 degrees slope in the uppermost part of late Quaternary well-bedded slope deposits. The failure zone extends from water depths of 374-510 m near the base of slope, occupies an area of 4 km 2 , and involved the translation of 0.01-0.02 km 3 of sediment. Major geomorphic features of the mudflow deposit include a headscarp 6-8 m high, a scar 50-700 m wide, and a main body 1 km long and 12 m thick. The hummocky surface of the mudflow deposits, their chaotic internal structure, and the bulbous toe tapering upslope to a thin tail are consistent with mass flow involving extensive internal deformation. Sediment failed in stages, ending with upslope retrogressive retreat of the headwall along the east side of the failure zone. Known sedimentation rates of 0.8-1.4 m/k.y., as well as the presence of a thin (0.15-0.5 m thick) sediment cap resting atop the scar surface, indicate that the failure probably occurred within the past few centuries. A geotechnical analysis incorporating the results of both static and dynamic triaxial strength tests shows that the failure was probably caused by a strong (M nearly equal 7.5) nearby earthquake. The weakened sediment that remained after earthquake shaking continued to flow down the gentle basin slope under the stresses generated by gravity alone. The analysis also shows that much of the slope sediment is marginally stable and that additional mudflows will probably occur during future strong seismic shaking. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.