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Intrastab Earthquakes: Dehydration of the Cascadia Slab

L.A. Preston·K. C. Creager·R. S. Crosson·T.M. Brocher·A.M. Trehu
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Abstract

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 intrastab earthquakes into two groups, permitting a new understanding of the origins of intrastab 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.

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L.A. Preston, K. C. Creager, R. S. Crosson, T.M. Brocher, A.M. Trehu. 2003. Intrastab Earthquakes: Dehydration of the Cascadia Slab. https://doi.org/10.1126/science.1090751

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