Imaging the source region of Cascadia tremor and intermediate-depth earthquakes

Abstract

Research Article| December 01, 2009 Imaging the source region of Cascadia tremor and intermediate-depth earthquakes Geoffrey A. Abers; Geoffrey A. Abers * 1Lamont-Doherty Earth Observatory of Columbia University, Route 9W, P.O. Box 1000, Palisades, New York 10964, USA *E-mail: abers@ldeo.columbia.edu. Search for other works by this author on: GSW Google Scholar Laura S. MacKenzie; Laura S. MacKenzie 2Schlumberger Data and Consulting Services 6501 S. Fiddler's Green, Greenwood Village, Colorado 80111, USA Search for other works by this author on: GSW Google Scholar Stéphane Rondenay; Stéphane Rondenay 3Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA Search for other works by this author on: GSW Google Scholar Zhu Zhang; Zhu Zhang 4Department of Geology and Geophysics, University of Wyoming, Laramie, Wyoming 82070, USA Search for other works by this author on: GSW Google Scholar Aaron G. Wech; Aaron G. Wech 5Department of Earth and Space Science, University of Washington, Seattle, Washington 98195, USA Search for other works by this author on: GSW Google Scholar Kenneth C. Creager Kenneth C. Creager 5Department of Earth and Space Science, University of Washington, Seattle, Washington 98195, USA Search for other works by this author on: GSW Google Scholar Geology (2009) 37 (12): 1119–1122. https://doi.org/10.1130/G30143A.1 Article history received: 16 Feb 2009 rev-recd: 17 Jul 2009 accepted: 21 Jul 2009 first online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Geoffrey A. Abers, Laura S. MacKenzie, Stéphane Rondenay, Zhu Zhang, Aaron G. Wech, Kenneth C. Creager; Imaging the source region of Cascadia tremor and intermediate-depth earthquakes. Geology 2009;; 37 (12): 1119–1122. doi: https://doi.org/10.1130/G30143A.1 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 SocietyGeology Search Advanced Search Abstract The subduction of hydrated oceanic crust releases volatiles that weaken the plate boundary interface, trigger earthquakes, and regulate transient phenomena such as episodic tremor and slip (ETS). It is not clear how dehydration can separately induce earthquakes within the subducting plate and ETS, partly because few data exist on their relationship to subduction zone structures. We present results of a seismic experiment in the Washington Cascades, United States, that images a region producing both earthquake types. Migration of scattered teleseis-mic waves provides images of low-velocity subducting crust at depths <40–45 km with sharp boundaries above and below it. The sharp upper boundary indicates a layer of weak sediment or an overpressured fault zone that terminates abruptly downdip at 40–45 km depth. Regular earthquakes are at the top of the mantle within the downgoing plate everywhere the plate is <95 km deep, but ETS only exists where the sharp upper boundary occurs. The ETS location supports models of slow slip that require near-lithostatic fluid pressure, whereas regular earthquakes nucleate closer to the origin of metamorphic dehydration. Very low shear stresses on the plate boundary may limit seismicity to ETS and similar phenomena. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.