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Pacific Coastal & Marine Science Center

Coastal and Marine Earthquake Studies

 

The Cascadia Megathrust and Tectonic Stress in the Pacific Northwest

Tectonic Setting and Stress Field

Pacific Northwest Tectonic SettingExplanation

Inward pointing red arrows: Orientation of principal compressive stress

Outward pointing red arrows: Orientation of principal tensional stress

Inward pointing green arrows: Orientation of principal compressive in Puget Sound

Yellow arrows: Relative plate motion between the oceanic plates (Pacific and Juan de Fuca) and the North American plate

Stress Provinces

Pacific Northwest Stress Province: N-S oriented compressive stress

Cascade Convergence Stress Province (CCP): NNE-SSW oriented compressive stress

Basin and Range Stress Province: E-W oriented tensional stress

Canadian Mid-Plate Stress Province: NE-SW oriented compressive stress

Questions

  1. Is the N-S oriented compressive stress in the Pacific Northwest Stress Province related more to Pacific-North America relative plate motion than Juan de Fuca-North America relative plate motion?
  2. Is the direction of stress in the Cascade Convergence Stress Province related to increase coupling along the subduction zone offshore of Washington?
(See Answers to these questions on another page.)