Location, structure, and seismicity of the Seattle fault zone, Washington: Evidence from aeromagnetic anomalies, geologic mapping, and seismic-reflection data

Abstract

Research Article| February 01, 2002 Location, structure, and seismicity of the Seattle fault zone, Washington: Evidence from aeromagnetic anomalies, geologic mapping, and seismic-reflection data Richard J. Blakely; Richard J. Blakely 1U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025, USA Search for other works by this author on: GSW Google Scholar Ray E. Wells; Ray E. Wells 1U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025, USA Search for other works by this author on: GSW Google Scholar Craig S. Weaver; Craig S. Weaver 2U.S. Geological Survey, University of Washington, Seattle, Washington 98195, USA Search for other works by this author on: GSW Google Scholar Samuel Y. Johnson Samuel Y. Johnson 3U.S. Geological Survey, Denver Federal Center, Denver, Colorado 80225, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Richard J. Blakely 1U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025, USA Ray E. Wells 1U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025, USA Craig S. Weaver 2U.S. Geological Survey, University of Washington, Seattle, Washington 98195, USA Samuel Y. Johnson 3U.S. Geological Survey, Denver Federal Center, Denver, Colorado 80225, USA Publisher: Geological Society of America Received: 26 Dec 2000 Revision Received: 09 Aug 2001 Accepted: 21 Aug 2001 First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (2002) 114 (2): 169–177. https://doi.org/10.1130/0016-7606(2002)114<0169:LSASOT>2.0.CO;2 Article history Received: 26 Dec 2000 Revision Received: 09 Aug 2001 Accepted: 21 Aug 2001 First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Richard J. Blakely, Ray E. Wells, Craig S. Weaver, Samuel Y. Johnson; Location, structure, and seismicity of the Seattle fault zone, Washington: Evidence from aeromagnetic anomalies, geologic mapping, and seismic-reflection data. GSA Bulletin 2002;; 114 (2): 169–177. doi: https://doi.org/10.1130/0016-7606(2002)114<0169:LSASOT>2.0.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 A high-resolution aeromagnetic survey of the Puget Lowland shows details of the Seattle fault zone, an active but largely concealed east-trending zone of reverse faulting at the southern margin of the Seattle basin. Three elongate, east-trending magnetic anomalies are associated with north- dipping Tertiary strata exposed in the hanging wall; the magnetic anomalies indicate where these strata continue beneath glacial deposits. The northernmost anomaly, a narrow, elongate magnetic high, precisely correlates with magnetic Miocene volcanic conglomerate. The middle anomaly, a broad magnetic low, correlates with thick, nonmagnetic Eocene and Oligocene marine and fluvial strata. The southern anomaly, a broad, complex magnetic high, correlates with Eocene volcanic and sedimentary rocks. This tripartite package of anomalies is especially clear over Bainbridge Island west of Seattle and over the region east of Lake Washington. Although attenuated in the intervening region, the pattern can be correlated with the mapped strike of beds following a northwest-striking anticline beneath Seattle. The aeromagnetic and geologic data define three main strands of the Seattle fault zone identified in marine seismic-reflection profiles to be subparallel to mapped bedrock trends over a distance of >50 km. The locus of faulting coincides with a diffuse zone of shallow crustal seismicity and the region of uplift produced by the M 7 Seattle earthquake of a.d. 900–930. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.