Distribution of the Pacific/North America motion in the Queen Charlotte Islands‐S. Alaska plate boundary zone

Abstract

We present GPS data that constrain the distribution of the relative Pacific/North America motion across the Queen Charlotte Islands‐Alaska Panhandle margin (NW North America). Velocities from a network of 22 campaign and permanent sites indicate that the Pacific/North America transpressive motion is mostly accommodated along the locked Queen Charlotte‐Fairweather Fault. A significant portion (6–7 mm/yr) of the relative plate motion is taken up by distributed dextral shear across a ∼200 km wide region of the margin. Two models have been proposed to describe how the Pacific/North America convergence is accommodated off the Queen Charlotte Islands: Internal shortening vs. underthrusting of the Pacific plate. Although the GPS data cannot discriminate between the models, they provide strong constraints on the convergence distribution. The significant non‐transient motion of GPS sites along the central British Columbia‐southern Alaska margin has implications for seismic hazard and tectonic evolution models of the Canadian Cordillera.