Active tectonics of the Seattle fault and central Puget Sound, Washington—Implications for earthquake hazards

Abstract

Research Article| July 01, 1999 Active tectonics of the Seattle fault and central Puget Sound, Washington—Implications for earthquake hazards Samuel Y. Johnson; Samuel Y. Johnson 1U.S. Geological Survey, M.S. 966, Box 25046, Denver Federal Center, Denver, Colorado 80225 Search for other works by this author on: GSW Google Scholar Shawn V. Dadisman; Shawn V. Dadisman 1U.S. Geological Survey, M.S. 966, Box 25046, Denver Federal Center, Denver, Colorado 80225 Search for other works by this author on: GSW Google Scholar Jonathan R. Childs; Jonathan R. Childs 2U.S. Geological Survey, M.S. 999, 345 Middlefield Road, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar William D. Stanley William D. Stanley 1U.S. Geological Survey, M.S. 966, Box 25046, Denver Federal Center, Denver, Colorado 80225 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1999) 111 (7): 1042–1053. https://doi.org/10.1130/0016-7606(1999)111<1042:ATOTSF>2.3.CO;2 Article history first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Samuel Y. Johnson, Shawn V. Dadisman, Jonathan R. Childs, William D. Stanley; Active tectonics of the Seattle fault and central Puget Sound, Washington—Implications for earthquake hazards. GSA Bulletin 1999;; 111 (7): 1042–1053. doi: https://doi.org/10.1130/0016-7606(1999)111<1042:ATOTSF>2.3.CO;2 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 SocietyGSA Bulletin Search Advanced Search Abstract We use an extensive network of marine high-resolution and conventional industry seismic-reflection data to constrain the location, shallow structure, and displacement rates of the Seattle fault zone and crosscutting high-angle faults in the Puget Lowland of western Washington. Analysis of seismic profiles extending 50 km across the Puget Lowland from Lake Washington to Hood Canal indicates that the west-trending Seattle fault comprises a broad (4–6 km) zone of three or more south-dipping reverse faults. Quaternary sediment has been folded and faulted along all faults in the zone but is clearly most pronounced along fault A, the northernmost fault, which forms the boundary between the Seattle uplift and Seattle basin. Analysis of growth strata deposited across fault A indicate minimum Quaternary slip rates of about 0.6 mm/yr. Slip rates across the entire zone are estimated to be 0.7–1.1 mm/yr.The Seattle fault is cut into two main segments by an active, north-trending, high-angle, strike-slip fault zone with cumulative dextral displacement of about 2.4 km. Faults in this zone truncate and warp reflections in Tertiary and Quaternary strata and locally coincide with bathymetric lineaments. Cumulative slip rates on these faults may exceed 0.2 mm/yr. Assuming no other crosscutting faults, this north-trending fault zone divides the Seattle fault into 30–40-km-long western and eastern segments. Although this geometry could limit the area ruptured in some Seattle fault earthquakes, a large event ca. A.D. 900 appears to have involved both segments. Regional seismic-hazard assessments must (1) incorporate new information on fault length, geometry, and displacement rates on the Seattle fault, and (2) consider the hazard presented by the previously unrecognized, north-trending fault zone. 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.