In 1788, presumably 2 earthquakes ruptured the Shumagin gap from Kodiak island westwards. The first earthquake, occurring on July 21th provides strong evidence for co-seismic uplift and tsunami deposits along the coasts of Kodiak Island. Sykes et al. (1980) assumed a 600km long rupture which would correspond to a Mw 8.9 earthquake using the empirical relationships of Thingbaijam et al. (2017). The second earthquake, of probably smaller magnitude is assumed to have occurred on August 6th, yet with less strong evidence.
For this earthquake, Sykes et al. (1980) describe various reports about landslides and tsunamis which affected Kodiak Island associated with strong shaking.