Late Cenozoic deformation in the Matanuska Valley, Alaska: Three-dimensional strain in a forearc region

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Research Article| May 01, 1981 Late Cenozoic deformation in the Matanuska Valley, Alaska: Three-dimensional strain in a forearc region RONALD L. BRUHN; RONALD L. BRUHN 1Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah 84112 Search for other works by this author on: GSW Google Scholar TERRY L. PAVLIS TERRY L. PAVLIS 1Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah 84112 Search for other works by this author on: GSW Google Scholar Author and Article Information RONALD L. BRUHN 1Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah 84112 TERRY L. PAVLIS 1Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah 84112 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1981) 92 (5): 282–293. https://doi.org/10.1130/0016-7606(1981)92<282:LCDITM>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation RONALD L. BRUHN, TERRY L. PAVLIS; Late Cenozoic deformation in the Matanuska Valley, Alaska: Three-dimensional strain in a forearc region. GSA Bulletin 1981;; 92 (5): 282–293. doi: https://doi.org/10.1130/0016-7606(1981)92<282:LCDITM>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 The Matanuska Valley is located in the forearc terrane of the Alaska-Aleutian volcanic arc. A period of extensive faulting occurred in the western Matanuska Valley during the Neogene. Faulting was a response to intraplate strain caused by subduction of the Pacific plate beneath the convergent margin. The Neogene fault system consisted of three sets of faults: two sets of north-trending strike-slip faults and a set of east-northeast–trending reverse faults. Three fault sets were required to accommodate the general three-dimensional deformation. Crustal shortening in a north-northwest direction was accompanied by lateral and vertical extension.The direction of maximum horizontal shortening strain has apparently been constant since the Neogene, although there is no evidence for extensive faulting of Quaternary deposits in the area we have studied. The western Matanuska Valley is located only 50 km above the Benioff zone, and the predicted maximum principal shortening direction is north-northwest, on the basis of the slip-vector azimuth between the North American and Pacific plates and the nature of surficial ground displacements during the 1964 (M = 8.4) subduction zone earthquake. Focal mechanisms for earthquakes in the vicinity of the Benioff zone and in the lower part of the North American plate indicate west-northwest extension and north-northeast shortening. This means that the strain field at depths below 20 km may differ significantly from the near-surface strain field. 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.