Rapid active thrust faulting at the northern Alaska Range front

Abstract Plate convergence rates strongly influence seismicity and mountain building inboard of convergent margins, but the distribution kinematics structures accommodating farfield can be elusive. In interior Alaska, Yakutat microplate drives late Pleistocene–recent right slip on Denali fault, westward-decreasing leave substantial residual motion unaccounted for. Here, we show that Northern Foothills thrust beneath northern Alaska Range absorbs a modern 4.4 mm/yr geodetic velocity gradient equivalent to ~78% 5.6 along central fault. Infrared-stimulated luminescence ages strath terrace deposits (67–4 ka; six sites) quantify Totatlanika River bedrock incision across 1947 Mw 7.1 earthquake epicentral region. Incision increase abruptly from <1 4.8–5.6 above blind tip near range front. Rapid at 6.7 steep ramp front accommodates gradient, rock uplift matching measured rates, implies large earthquakes like event may recur with 500–1400 yr frequency. Results illuminate focused seismogenic strain complex margin prompt reevaluation Alaska’s neotectonic framework.