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Science 14 October 1994:
Vol. 266. no. 5183, pp. 237 - 243
DOI: 10.1126/science.266.5183.237
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Articles

Crustal Architecture of the Cascadia Forearc

A. M. Trehu 1, I. Asudeh 2, T. M. Brocher 3, J. H. Luetgert 3, W. D. Mooney 3, J. L. Nabelek 1, and Y. Nakamura 4

1 Department of Oceanic and Atmospheric Sciences, Oceanography Administration Building 104, Oregon State University, Corvallis, OR 97331, USA.
2 Geological Survey of Canada, 1 Observatory Crescent, Ottawa, Ontario, Canada K1A 0Y3
3 U.S. Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025, USA.
4 Institute for Geophysics, University of Texas, 8701 North Mopac Boulevard, Austin, TX 78759, USA.

Seismic profiling data indicate that the thickness of an accreted oceanic terrane of Paleocene and early Eocene age, which forms the basement of much of the forearc beneath western Oregon and Washington, varies by approximately a factor of 4 along the strike of the Cascadia subduction zone. Beneath the Oregon Coast Range, the accreted terrane is 25 to 35 kilometers thick, whereas offshore Vancouver Island it is about 6 kilometers thick. These variations are correlated with variations in arc magmatism, forearc seismicity, and long-term forearc deformation. It is suggested that the strength of the forearc crust increases as the thickness of the accreted terrane increases and that the geometry of the seaward edge of this terrane influences deformation within the subduction complex and controls the amount of sediment that is deeply subducted.


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Seismic evidence for widespread serpentinized forearc upper mantle along the Cascadia margin.
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Forearc Deformation and Great Subduction Earthquakes: Implications for Cascadia Offshore Earthquake Potential.
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