A Reevaluation of the 1958 Fairweather, Alaska, Earthquake Sequence

I have relocated aftershocks, performed waveform modeling, and modeled induced Coulomb failure stress to better determine rupture extent and controls on the rupture process of the 1958 Fairweather earthquake sequence in southeastern Alaska. I estimate a fault rupture length range from 260 km (source time function duration) to 370 km (aftershock zone length). I estimate an average slip of 3.5 m from waveform modeling, comparable to measured surface (2-3.5 m) slip. The largest pulses of moment release along the Fairweather fault zone may have occurred near Lituya Bay, where a huge landslide and subsequent water wave were produced, and near Dry Bay, the location of the mainshock's intensity center. The region of high moment release near Lituya Bay correlates with a gravity high located northeast of the fault zone. Coulomb failure modeling suggests aftershocks were most likely to have occurred on northwest striking reverse faults. These new source parameters indicate the 1958 mainshock was comparable in size to the 2002 M 7.9 Denali fault earthquake and shared other similarities with the 2002 event.