07/21/1788 | 1788 Kodiak Island Earthquake


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.

Events in the same region
Date Title Region Preferred Magnitude Quality*
1788 Jul 21st 1788 Kodiak Island Earthquake Alaska 8.6 C
1788 Aug 06th 1788 Shumagin Earthquake Alaska 8.3 C
  • NGDC - - Link
  • Sykes et al (1981) -Sykes, Lynn R., et al. "Rupture zones of great earthquakes in the Alaska-Aleutian arc, 1784 to 1980." Science 210.4476 (1980): 1343-1345. - Link
Event Characteristics
Preferred Magnitude 8.60 (8.00-8.60)
Epicenter 57.000°N, -153.000°E
Depth unknown
Tsunami yes
Paleo-Event no
Quality of Evidence C

Magnitude Range
Year Reference Magnitude
2010 NGDC 8
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.