Cascadia Subduction Zone - Main Points

1.     Cascade Subduction zone

• Juan de Fuca plate is subducting beneath North America

• Result: formation of the Coast Range, Willamette Valley and Cascade volcanoes and seismic zone

2.      Fault Plane solution

• right-lateral transform faults indicate the Pacific plate is moving north

• seismically active region although no large (>8 magnitude) historic earthquakes

3.     Geodetic data

• Oregon and Washington are generally moving in a NNE direction at rate of 8-10mm/year

• Juan de Fuca plate is subducting at a rate of 37mm/year 

4.      Silent slip event

• 1999 event indicating a locked section of the Juan de Fuca and North American plates

• Coseismic uplift measured at many GPS stations

5.    Olympic Mountains

• formed from accretion on to North America

• uplifted from buckling of the Juan De Fuca plate, due to the curvature of the subduction zone

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