Current deformation in the northern Canadian Cordillera inferred from GPS measurements

Continuous and campaign-style Global Positioning System (GPS) measurements provide new constraints on the first-order current deformation pattern of the northern Cordillera of NW Canada and eastern Alaska. The Yakutat block is currently colliding with North America in the corner of the Gulf of Alaska. Our data infer that relative Yakutat - North America motion is accommodated across the eastern boundary by right-lateral motion (similar to 40 mm/a), mainly on the Fairweather fault, and minor shortening (similar to 6 mm/a). To the north, collision is taken up by shortening (similar to 31 mm/a) mainly on the Chugach-St. Elias fault system, with westward extrusion and possible counterclockwise rotation of the Yakutat block and Alaskan fore arc facilitated by similar to 23 mm/a right-lateral motion that is shared by several faults. The seismicity pattern indicates that plate boundary deformation is far reaching, producing strain throughout eastern Alaska, Yukon, and western Northwest Territories. Our GPS data confirm the transfer of strain from the Yakutat collision zone and enable the extent of plate boundary deformation to be mapped, thereby defining the western edge of "stable'' North America. GPS sites in SW Yukon show motion of 3 - 10 mm/a to the NE, confirming that strain is transferred at least 400 km from the Yakutat collision. Continued transfer north toward the Mackenzie Delta and NE to the Mackenzie Mountains, indicated by current seismicity, is not yet well resolved by the campaign GPS data, which are hampered by coseismic and postseismic effects of the 2002 M-w 7.9 earthquake on the Denali fault in eastern Alaska.