The St. Elias earthquake of February 28, 1979 and two earlier earthquakes in the St. Elias Range, Alaska, are shown to have involved thrust motion on gently NNW-dipping faults associated with subduction of the Pacific beneath the North American Plate. The space-time patterns of the seismicity located within and in the immediate vicinity of the rupture zone of the St. Elias event in the 16-yr period prior to it, indicate approximately 6.3 yr of relative quiescence before the main shock, interrupted by a burst of seismic activity about 3 yr prior to the event. This observed seismic pattern resembles those reported for other large earthquakes, and therefore, we suggest that the preceding burst of activity may have been a precursor.

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