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.
|1788 Jul 21st||1788 Kodiak Island Earthquake||Alaska||8.6||C|
|1788 Aug 06th||1788 Shumagin Earthquake||Alaska||8.3||C|
|Preferred Magnitude||8.60 (8.00-8.60)|
|Quality of Evidence||C|
|1981||Sykes et al (1981)||8.6|
This table lists some of the most relevant publications in estimating the moment magnitude of this earthquake. If you think there are other important or new publications, please get in contact.