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Science 14 November 2003:
Vol. 302. no. 5648, pp. 1197 - 1200
DOI: 10.1126/science.1090751
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Reports

Intraslab Earthquakes: Dehydration of the Cascadia Slab

Leiph A. Preston,1* Kenneth C. Creager,1 Robert S. Crosson,1 Thomas M. Brocher,2 Anne M. Trehu3

We simultaneously invert travel times of refracted and wide-angle reflected waves for three-dimensional compressional-wave velocity structure, earthquake locations, and reflector geometry in northwest Washington state. The reflector, interpreted to be the crust-mantle boundary (Moho) of the subducting Juan de Fuca plate, separates intraslab earthquakes into two groups, permitting a new understanding of the origins of intraslab earthquakes in Cascadia. Earthquakes up-dip of the Moho's 45-kilometer depth contour occur below the reflector, in the subducted oceanic mantle, consistent with serpentinite dehydration; earthquakes located down-dip occur primarily within the subducted crust, consistent with the basalt-to-eclogite transformation.

1 Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195, USA.
2 U.S. Geological Survey, Menlo Park, CA 94025, USA.
3 College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA.

* To whom correspondence should be addressed. E-mail: preston{at}ess.washington.edu

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
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Cascadia Tremor Located Near Plate Interface Constrained by S Minus P Wave Times.
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Low Potential for Large Intraslab Earthquakes in the Central Cascadia Subduction Zone.
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