Field observations made ten years after the southeast Alaska earthquake (M = 7.9) of 10 July 1958 reveal environmental and geomorphic changes in the Fairweather fault zone. Faulting associated with the earthquake killed many trees in the Crillon Lake region. Trees were tilted and later fell, and possibly were drowned because of changes in drainage conditions. A nearly vertical, 2-meter scarp in soil has been eroded to a slope of 35° to 40° in the decade since 1958.
Microearthquake activity sampled at a single site on the fault is at least equal to or possibly greater than that reported from active sites on the San Andreas and Denali faults. The distribution of S-P times is consistent with a uniform planar distribution of shocks on a segment of the fault that slipped in 1958. The expected seismicity from aftershocks of the 1958 earthquake is less, but not significantly less, than the observed seismicity.