Rapid resetting of an estuarine recorder of the 1964 Alaska earthquake

Abstract

Research Article| September 01, 2001 Rapid resetting of an estuarine recorder of the 1964 Alaska earthquake Brian F. Atwater; Brian F. Atwater 1U.S. Geological Survey at Department of Earth and Space Sciences, University of Washington, Seattle, Washington 98195-1310, USA Search for other works by this author on: GSW Google Scholar David K. Yamaguchi; David K. Yamaguchi 25630 200th Street S.W., #202B, Lynnwood, Washington 98036-6260, USA Search for other works by this author on: GSW Google Scholar Stein Bondevik; Stein Bondevik 3Department of Geology, University of Tromsø, N-9073 Tromsø, Norway Search for other works by this author on: GSW Google Scholar Walter A. Barnhardt; Walter A. Barnhardt 4U.S. Geological Survey, M.S. 999, 345 Middlefield Road, Menlo Park, California 94025, USA Search for other works by this author on: GSW Google Scholar Lorin J. Amidon; Lorin J. Amidon 5Department of Earth Sciences, Dartmouth College, Hanover, New Hampshire 03755-3571, USA Search for other works by this author on: GSW Google Scholar Boyd E. Benson; Boyd E. Benson 6GeoEngineers, Inc., 8410 154th Avenue N.E., Redmond, Washington 98052, USA Search for other works by this author on: GSW Google Scholar Gudrun Skjerdal; Gudrun Skjerdal 7Department of Geology, University of Tromsø, N-9073 Tromsø, Norway Search for other works by this author on: GSW Google Scholar John A. Shulene; John A. Shulene 8928 11th Avenue S.W., Puyallup, Washington 98371, USA Search for other works by this author on: GSW Google Scholar Futoshi Nanayama Futoshi Nanayama 9Active Fault Research Center, National Institute for Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8567, Japan Search for other works by this author on: GSW Google Scholar GSA Bulletin (2001) 113 (9): 1193–1204. https://doi.org/10.1130/0016-7606(2001)113<1193:RROAER>2.0.CO;2 Article history received: 02 May 2000 rev-recd: 27 Nov 2000 accepted: 22 Dec 2000 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 Brian F. Atwater, David K. Yamaguchi, Stein Bondevik, Walter A. Barnhardt, Lorin J. Amidon, Boyd E. Benson, Gudrun Skjerdal, John A. Shulene, Futoshi Nanayama; Rapid resetting of an estuarine recorder of the 1964 Alaska earthquake. GSA Bulletin 2001;; 113 (9): 1193–1204. doi: https://doi.org/10.1130/0016-7606(2001)113<1193:RROAER>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 Tides and plants have already restored much of a landscape that the 1964 Alaska earthquake destroyed. At the head of a macrotidal estuary near Anchorage, in the vicinity of Portage, subsidence during the earthquake changed meadows, thickets, and spruce groves into barren tidal flats. Tidal-flat silt and sand soon buried the pre- earthquake landscape while filling intertidal space that the subsidence had made. The flats supported new meadows and thickets by 1973 and new spruce by 1980. Three new findings confirm that the flats aggraded rapidly and that their vegetation is maturing. (1) Most of the postearthquake deposits at Portage date from the first decade after the 1964 earthquake. Their thickness of 23 sites in a 0.5 km2 area was 1.4 ± 0.2 m in 1973, 1.6 ± 0.2 m in 1991, and 1.6 ± 0.3 m in 1998. (2) Many of the deposits probably date from the first months after the earthquake. The deposits contain sedimentary couplets in which coarse silt or very fine sand is capped by fine or medium silt. About 100 such couplets make up the lowest 0.5 m or more of the postearthquake deposits in two outcrops. These couplets thicken and thin rhythmically, both as groups of 5–20 couplets and as pairs of successive couplets. Probably, the groups of thick couplets represent the highest tides, the groups of thin couplets represent some of the lesser high tides, and the pairs record inequality between twice-daily high tides. (3) In the 1980s and 1990s, thickets expanded and spruce multiplied. The vegetation now resembles the fossil assemblage rooted in the buried landscape from 1964.Had the 1964 Alaska earthquake been repeated a decade later, the two earthquakes would now be recorded by two superposed, buried landscapes near Portage. Much more than a decade is probably needed to reset similar recorders at mesotidal estuaries of the Cascadia subduction zone. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.