A Block Model of Present‐Day Kinematics of Alaska and Western Canada

Abstract

AbstractWe present an updated GPS velocity field for Alaska and western Canada and use it to develop the first regionally comprehensive tectonic block model for the area based on modern geodetic data. The greatest tectonic influences along the southern margin are the translation, collision, and flat slab subduction of the Yakutat block and subduction of the Pacific plate. Northward directed velocities surrounding the Yakutat collisional front are consistent with indenter‐related deformation while southcentral Alaska is undergoing a counterclockwise rotation. Westerly velocities in western Alaska and along the Aleutian forearc suggest that crustal material is escaping into the Bering Sea region. The majority of relative plate motion is taken up along major boundary faults, but right‐lateral strike‐slip faults in interior and western Alaska accommodate part of the motion. Escape tectonics in western Alaska extends as far north as the Kaltag fault. We observe significant motion relative to North America in every part of Alaska, including the North Slope. Evidence of localized right‐lateral shear between the Totschunda and Fairweather faults suggests that strain transfer into interior Alaska has moved away from the eastern Denali‐Chatham Strait system to a more direct corridor. Observed deformation in southcentral Alaska indicates that locked portions of the Yakutat flat slab extend further east and north than previously estimated.