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Northward migration of the Cascadia forearc in the northwestern U.S. and implications for subduction deformation

Earth, Planets and Space
By:  and 
https://doi.org/10.1186/BF03352384

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Abstract

Geologic and paleomagnetic data from the Cascadia forearc indicate long-term northward migration and clockwise rotation of an Oregon coastal block with respect to North America. Paleomagnetic rotation of coastal Oregon is linked by a Klamath Mountains pole to geodetically and geologically determined motion of the Sierra Nevada block to derive a new Oregon Coast—North America (OC-NA) pole of rotation and velocity field. This long-term velocity field, which is independent of Pacific Northwest GPS data, is interpreted to be the result of Basin-Range extension and Pacific-North America dextral shear. The resulting Oregon Coast pole compares favorably to those derived solely from GPS data, although uncertainties are large. Subtracting the long-term motion from forearc GPS velocities reveals ENE motion with respect to an OC reference frame that is parallel to the direction of Juan de Fuca-OC convergence and decreases inland. We interpret this to be largely the result of subduction-related deformation. The adjusted mean GPS velocities are generally subparallel to those predicted from elastic dislocation models for Cascadia, but more definitive interpretations await refinement of the present large uncertainty in the Sierra Nevada block motion.

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Publication type Article
Publication Subtype Journal Article
Title Northward migration of the Cascadia forearc in the northwestern U.S. and implications for subduction deformation
Series title Earth, Planets and Space
DOI 10.1186/BF03352384
Volume 53
Issue 4
Year Published 2001
Language English
Publisher Springer
Description 9 p.
First page 275
Last page 283
Country Canada, United States
State British Columbia, Washington
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