Late Cenozoic offsets on the offshore connection between the Fairweather and Queen Charlotte faults off southeast Alaska

Closely spaced seismic reflection profiles permit us to extend the onshore Fairweather fault across the continental margin off southeast Alaska to the Queen Charlotte fault. Evidence for Quaternary movement along this major plate boundary includes 20-40-m high sea-floor scarps, offset subsurface seismic reflectors, sea-floor bathymetry that indicates as much as 70 km of right-lateral offset in the last 1 m.y., 5-6 cm/yr of movement on the onshore Fairweather fault, and recorded seismicity along the fault. The Fairweather-Queen Charlotte fault system, similar in dimension to the San Andreas fault system, is a dextral transform fault that truncates the continental margin of North America. Much of the late Cenozoic motion between the Pacific and North American plates has been taken up along the fault system. The Fairweather-Queen Charlotte fault evolved to its present form after passage of the Yakutat block, the youngest of the allochthonous terranes that form southern Alaska. ?? 1988.