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Paleomagnetic and GPS data indicate that Washington and Oregon have rotated clockwise for the past 16 Myr.
Late Cenozoic and Quaternary fault geometries, seismicity lineaments, and focal mechanisms provide evidence that this rotation is accommodated by north directed thrusting and right-lateral strike-slip faulting in Washington, and SW to W directed normal faulting and right-lateral strike-slip faulting to the east.
Several curvilinear NW to NNW trending high-angle strike-slip faults and seismicity lineaments in Washington and NW Oregon define a geologic pole (117.7°W, 47.9°N) of rotation relative to North America. Many faults and focal mechanisms throughout northwestern U.S. and southwestern British Columbia have orientations consistent with this geologic pole as do GPS surface velocities corrected for elastic Cascadia subduction zone coupling.
Large Quaternary normal faults radial to the geologic pole, which appear to accommodate crustal rotation via crustal extension, are widespread and can be found along the Lewis and Clark zone in Montana, within the Centennial fault system north of the Snake River Plain in Idaho and Montana, to the west of the Wasatch Front in Utah, and within the northern Basin and Range in Oregon and Nevada.
Distributed strike-slip faults are most prominent in western Washington and Oregon and may serve to transfer slip between faults throughout the northwestern U.S.
This space is for temporary chat only and all posts drop off automatically and are not saved.
Members with real questions or comments that need an actual response, please post on the main forum - not here! Casual PG-13 posts only, no politics or religion please!
dillonf: RickB that is hilarious
Mar 20, 2024 19:34:30 GMT -5
RickB: Alarming fact: USA's national vasectomy rate increases each year during college basketball's March Madness. The nets folks, snip the nets.
Mar 22, 2024 6:00:35 GMT -5
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1dave: I spy with my little eye .
Mar 22, 2024 8:53:33 GMT -5
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Welcome to the Rock Tumbling Hobby Forum where we share a love of rocks and a sense of community as enduring as the stones we polish.
The RTH Forum of www.RockTumbling.com is an Amazon Associate site and we earn money from
qualifying purchases you make after clicking on our links such as this
Rock Tumbling Supplies on Amazon
link for instance, or any of our various product ads and banners. By clicking our links every time you begin your Amazon shopping
experience, you are generating a bit of revenue for the forum which helps us cover our expenses. Thank you for your support!