Structure of the Lithosphere in a Young Subduction Zone: Results from Reflection and Refraction Studies

  1. Muawia Barazangi and
  2. Larry Brown
  1. Ron M. Clowes,
  2. George D. Spence,
  3. Robert M. Ellis and
  4. David A. Waldron

Published Online: 15 MAR 2013

DOI: 10.1029/GD014p0313

Reflection Seismology: The Continental Crust

Reflection Seismology: The Continental Crust

How to Cite

Clowes, R. M., Spence, G. D., Ellis, R. M. and Waldron, D. A. (1986) Structure of the Lithosphere in a Young Subduction Zone: Results from Reflection and Refraction Studies, in Reflection Seismology: The Continental Crust (eds M. Barazangi and L. Brown), American Geophysical Union, Washington, D. C.. doi: 10.1029/GD014p0313

Author Information

  1. Department of Geophysics and Astronomy, University of British Columbia, Vancouver

Publication History

  1. Published Online: 15 MAR 2013
  2. Published Print: 1 JAN 1986

Book Series:

  1. Geodynamics Series

ISBN Information

Print ISBN: 9780875905143

Online ISBN: 9781118670118

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Keywords:

  • Earth—Crust—Congresses;
  • Continents—Congresses;
  • Seismic reflection method—Congresses

Summary

Vancouver Island, on the west coast of Canada, is believed to have formed through the process of accretionary tectonics and represents a dispersed block of the Wrangellia terrane. Presently, the oceanic Juan de Fuca plate is subducting beneath the continental plate, A series of refraction and reflection experiments has been carried out to provide better delineation of lithospheric structure in this complex zone of convergence. An offshore-onshore refraction profile has enabled development of a lithospheric model from the deep ocean to near the volcanic arc. Seaward of the continental slope, the plate which includes a 9 km thick crust dips ∼1° landward; below the slope the angle of dip increases to ∼3°; and below the continental shelf it increases substantially to ∼15°. At depths of 30 to 40 km below the shelf, a landward-dipping upper mantle boundary has been inferred from wide-angle reflection phases, and is interpreted as the base of the subducting oceanic lithosphere. In the overlying continental crust a large block of high velocity (∼7.7 km/s) material is embedded and may represent a detached remnant of subducted slab. A test multichannel explosion profile shows reflections to two-way traveltimes of 11 s; four reflectors correspond closely to boundaries in the refraction model. A 1984 follow-up Vibroseis program has produced high quality data, which, combined with the refraction data, illustrate the complementary nature of the two data sets.