부산대학교 도서관

We utilize 3‐D finite element geodynamic models, incorporating long‐term kinematic estimates of upper plate motion, to better understand the roles that viscosity structure and mantle tractions play in generating plate motions and continental interior deformation in Alaska. Surface deformation in the Pacific‐North American plate boundary zone in Alaska and northwest Canada is strongly influenced by the complex interactions between flat‐slab subduction, gravitational collapse and mantle tractions. Predictions of long‐term tectonic block motion derived from recent Global Positioning System datasets (GPS) reveal surface motions atypical of other continental convergent plate boundary zones. Specifically, in northern and northwestern Alaska, southeastward motion is observed directed back toward the plate boundary. Geodynamic models that incorporate a southeastward directed long‐wavelength mantle traction of ∼2.5–3.8 MPa best replicate surface velocities in Alaska. These mantle tractions, in conjunction with the collision of the Yakutat microplate, appear to drive the uplift and deformation in the Mackenzie Mountains. Furthermore, the extent of the northward motion in southern and central Alaska is controlled by the location of the leading edge of the Yakutat flat slab. Plain Language Summary: Plate motion estimates, derived from GPS measurements, indicate surface motions in Alaska are not typically observed in other convergent plate boundaries. As the Pacific plate and the Yakutat oceanic plateau collide and subduct beneath the continent, much of southern Alaska is forced to the northwest. However, in northern Alaska, southeastward movement is observed countering the motion from the south. We construct 3‐D computer models, based on the plate motion estimates, of the earth's crust and upper mantle to better understand how earth structure and forces due to mantle flow impact continental deformation in Alaska. Models with a southeastward directed long‐wavelength mantle flow best replicate the observed surface motion estimates. The mantle flow, in conjunction with the collision of the Yakutat oceanic plateau, appears to drive the uplift and deformation observed in the Mackenzie Mountains of northwestern Canada. Also, the extent of northward motion in southern and central Alaska is controlled by the location of the leading edge of the very shallowly subducting Yakutat oceanic plateau. Key Points: Models incorporating southeastward‐directed mantle traction of ∼2.5–3.8 MPa best replicate observed surface velocities throughout interior AlaskaUplift and deformation in the Mackenzie Mountains are driven by the impact of the Yakutat microplate in conjunction with basal tractionsThe extent of the northward motion in south‐central Alaska is controlled by the leading edge of the subducting Yakutat flat slab [ABSTRACT FROM AUTHOR]